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http://www.archive.org/details/courseoflecturesOOabborich 


COURSE  OF  LECTURES 


UPON  THB 


DEFENCE 


siA-coAST  OF  m  irao  states 


DELIVERED  BEFORE  THE 


U.  S.  NAVAL  WAE  COLLEGE 


BVT.  BRIG.-GEN.  HENRY  L  ABBOT,  U.  S.  ARMY 

Colonel  Corps  of  Engineers 


NOVEMBEE,  1887 


NEW  YORK 
D.    VAN    JSrOSTI^AND 

23  MUKRAY  AND  27  WARREN  STREET 
1888 


Copyright,  1888, 
Bt  W.  H.  FARRINGTON". 

^33  4^/ 


CONTENl'S. 


FIRST  LECTURE. 

GENERAL   CONSIDERATIONS. 

Introduction — The  Art  of  War  as  Applied  to  Coast  Defence  ;  Strat- 
egy; Grand  Tactics  ;  Logistics  ;  Art  of  the  Engineer — Proba- 
ble Nature  of  the  Attack  ;  Needful  Calibres  ;  Number  of  Guns; 
Guns  Ashore  and  Guns  Afloat ;  Naval  Tactics  against  Forts 5-40 

SECOND  LECTURE. 

ECONOMY  IN  COAST  DEFENCE. 

Limit  of  Judicious  Outlay — Economic  Value  of  Different  Elements; 
General  Analysis  ;  Case  of  Non- Disappearing  Barbette  Mount- 
ing; Case  of  the  King  Mounting  for  50-Ton  12-Inch  Rifles;  Case 
of  the  Duane  Lift ;  Case  of  an  Armored  Casemate  ;  Case  of  a 
Revolving  Turret ;  General  Conclusions 41-6G 

THIRD  LECTURE.  ^ 

SELECTING   THE   SITE  ;   HORIZONTAL   FIRE. 

Sites  to  Prevent  Bombardment  or  to  Cover  Anchorages — Sites  to 
Prevent  a  Forced  Passage  ;  Height  and  Character  of  the  Posi- 
tion ;  Development  of  Front ;  Submarine  Mine  Requirements — 
Horizontal  Fire  ;  Range  and  Position  Finders  ;  Revolving  Tur- 
rets ;  Armored  Casemates  ;  Lifts  ;  Disappearing  Gun  Batteries; 
Non-Disappearing  Gun  Batteries  ;  Flanking  Guns  for  Mined 
Zones  ;  Magazines 67-101 

FOURTH  LECTURE. 

MORTARS  AND  SUBMARINE  MINES. 

Vertical  Fire  ;  Advantages  of  Rifling  ;  Carriages  and  Platforms  ; 
Mortar  Batteries  ;  Economy  of  Mortars— Submarine  Mines  ; 
General  Conditions  ;  Attacks  by  Daylight  ;  Attacks  by  Night  or 
in  Fogs  ;  Attempted  Passage  by  Force 102-134 

FIFTH  LECTURE. 

SEA-COAST  FORTRESSES. 

Historical  Resumfi  of  Coast  Defence  in  America— Resistance  to 
Projectiles  ;  Armor  ;  Masonry  ;  Earth — Approximate  Formu- 
lae—Fortification  of  the  Site  Selected— Naval  Co-operation.  135-1 64 


First  Lecture, 


GENERAL  CONSIDERATIONS. 

Introduction— The  art  of  war  as  applied  to  Coast  Defence  ;  strategy  ; 
grand  tactics  ;  logistics  ;  art  of  the  Engineer — Probable  nature  of 
the  attack  ;  needful  calibres  ;  number  of  guns  ;  guns  ashore  and 
guns  afloat  ;  naval  tactics  against  forts. 

In  accepting  the  invitation  to  lecture  before  the 
Naval  War  College  on  our  Coast  Defences,  I  duly- 
appreciated  not  only  the  courtesy  extended  by  it  to 
the  body  of  Military  Engineers  which  I  represent,  but 
also  the  assistance  to  be  received  from  an  interchange 
of  views  upon  debatable  points  where  the  duties  of 
the  land  and  naval  forces  follow  parallel  lines  and 
demand  mutual  co-operation  of  the  most  cordial 
character.  Good  cannot  fail  to  result  from  dropping 
occasionally  the  technical  study  of  our  respective 
specialties,  and  taking  a  general  view  of  what  is 
needed  by  the  country  to  prevent  its  thousands  of 
miles  of  coast  line  from  opening  to  an  enemy  modes 
of  attack  where  heavy  blows  may  be  delivered  with 
little  risk,  and  where  decisive  results  may  be  at- 
tained without  affording  us  a  chance  of  bringing  our 
power  as  a  nation  to  bear. 

The  great  mass  of  our  population  is  now,  and 
from  the  nature  of  things  must  remain,  ignorant  of 
the  requirements  of  National  Defence.  The  duty  of 
considering  what  should  be  done,  and  how  it  should 
be  done,  has  been  devolved  upon  a  little  band  of  pro- 
fessional Army  and  Navy  men,  largely  graduates  of 
West  Point  and  Annapolis,  small  in  numbers  and 


6  General  Considerations. 

with  no  ready  mode  of  interchanging  views.  Yet  we 
are  expected  to  elaborate  a  wise  and  comprehensive 
system  of  coast  defence ;  and  when  the  evil  day 
comes  we  shall  justly  and  mercilessly  be  held  re- 
sponsible if,  blinded  by  professional  technicalities, 
we  have  failed  to  grasp  the  problem  in  its  entirety. 
We  are  too  much  tempted  to  forget  that  our  respon- 
sibility is  by  no  means  limited  to  details.  We  are 
expected  to  form  broad  and  harmonious  views  of 
what  the  Nation  needs  ;  and  only  in  this  way  shall 
we  secure  for  our  opinions  that  weight  which  unan- 
imity among  experts  always  carries  with  intelligent 
men  who  feel  themselves  to  lack  technical  informa- 
tion. What  the  Army  and  Navy  agree  in  recom- 
mending will  not  be  lightly  thrust  aside  ;  and  I  know 
of  no  better  mode  of  inducing  unanimity  of  opinion 
than  the  plan  of  mutual  co-operation  in  study  intro- 
duced by  the  founders  of  the  Naval  War  College. 

In  preparing  these  lectures  I  have  borne  in  mind 
the  professional  character  of  the  audience,  which 
wrould  render  details  on  such  subjects  as  modern 
^uns,  modern  armor,  modern  torpedoes,  and  subma- 
Tine  mines  as  wearisome  as  a  twice-told  tale  ;  they 
will  only  be  touched  upon  when  necessary  to  make 
my  meaning  clear.  On  the  other  hand,  it  would  tax 
your  patience  to  spend  time  in  elaborating  details  of 
land  construction,  such  as  foundations,  strength  of 
materials,  and  other  technicalities  of  the  profession 
which,  of  vital  importance  to  the  constructor,  can 
have  no  interest  to  a  naval  officer.  In  a  word,  I  shall 
try  to  present  the  general  subject  of  Coast  Defence 
from  the  point  of  view  of  an  Army  Engineer,  omit- 
ting technicalities  with  which  you  are  familiar  and 
also  those  in  which  you  have  no  interest.  In  return 
I  shall  be  grateful  for  suggestions  as  to  any  matters 
which  may  appear  doubtful  as  seen  from  a  naval 
point  of  view. 


Art  of  War  Applied  to  Coast  Defence, 


THE  ART  OF  WAR  AS  APPLIED  TO  COAST  DEFENCE. 

General  Brialmont  justly  observes  in  his  latest 
treatise  on  Fortification  that  the  defence  of  a  sea-coast 
resembles  that  of  a  chain  of  rugged  mountains.  At 
most  points  it  is  unassailable.  The  few  deep  bays 
and  mouths  of  rivers,  which  have  attracted  commerce 
and  caused  the  erection  of  cities  and  the  establish- 
ment of  dock-yards  and  naval  stations,  are  like  the 
natural  passes  through  the  mountains  that  have 
created  the  roads  and  villages  by  which  the  enemy 
must  move  to  the  attack. 

There  is,  however,  a  marked  difference  in  the  na- 
ture of  this  attack.  The  army  advances  like  a  swarm 
of  ants,  imposing  in  numbers  but  weak  in  individual 
power ;  the  fleets  approach  like  a  platoon  of  ele- 
phants in  the  days  of  Alexander,  terrible  as  individ- 
uals, but  few  in  number  and  handicapped  by  difficul- 
ties in  the  use  of  their  weapons. 

It  is  only  two  centuries  since  admirals  stepped 
from  the  qaarter-deck  to  command  armies  in  the 
field,  and  since  generals  won  victories  upon  the 
water  by  applying  land  tactics.  The  Services  have 
long  been  distinct,  but  it  does  not  follow  that  we 
may  not  still  derive  mutual  benefit  by  approaching 
this  problem  of  coast  defence  from  our  different 
standpoints,  and  applying  principles  learned  in  dif- 
ferent fields  of  duty. 

This  is  the  more  true  because  works  of  coast  de- 
fence are  less  a  matter  of  pure  fortification  than  an 
application  of  technical  details  which  are  becoming 
more  complex  from  year  to  year.  The  Engineer 
charged  with  planning  them  is  compelled  to  study 
the  subject  somewhat  from  a  naval  standpoint,  be- 
cause the  arrangements  of  all  defensive  works  are 
regulated  by  the  mode  of  attack;  and  the  latter, 
which  has  undergone  radical  changes  in  the  last  few 


8  General  Considerations. 

years,  is,  in  the  absence  of  actual  experience  in  war, 
still  far  from  being  detinitely  established.  Neverthe- 
less, in  its  general  features,  Coast  Defence  is  a  prob- 
lem to  which  many  rules  derived  from  land  opera- 
tions are  applicable. 

The  Art  of  War  is  usually  subdivided  by  military 
writers  into  five  principal  branches  :  Strategy,  Grand 
Tactics,  Logistics,  Elementary  Tactics,  and  the  Art 
of  the  Engineer.  Kules  of  each  of  these  branches, 
except  perhaps  of  Elementary  Tactics,  find  an  appli- 
cation more  or  less  important  in  the  problem  of  Sea- 
Coast  Defence. 

Strategy. — The  art  of  making  war  upon  the 
map  is  especially  concerned  with  the  selection  of  the 
points  for  permanent  occupation,  and  with  the  opera- 
tions of  the  fleets  which  in  coast  defence  represent 
the  movable  forces  of  the  Nation.  No  principles  are 
better  established  than  (1)  that  the  mass  of  our  forces 
should  be  thrown  upon  fractions  of  the  enemy  ;  (2) 
that,  so  far  as  practicable,  we  should  operate  upon 
his  communications  without  endangering  our  own  ; 
(3)  that  the  effort  should  be  energetic  and  in  concert 
throughout  the  theatre  of  war  ;  and  (4)  that  even  in 
a  defensive  campaign  vigorous  offensive  operations 
should  never  be  neglected  when  practicable. 

Every  principle  of  strategy  is  therefore  violated 
in  adopting  for  sea-coast  defence  a  plan  which  con- 
templates the  leaving  of  our  important  strategic  po- 
sitions without  permanent  fortifications,  and  looking 
to  defending  them  by  fractions  of  our  Navy  shut  up 
in  them  at  the  outbreak  of  war.  Such  a  project 
would  find  its  parallel  in  an  army  subdivided,  in- 
terned in  strong  places,  and  left  to  be  overmastered 
successively  by  the  united  strength  of  the  enemy. 
All  experience  in  land  campaigns  warns  us  that  by 
such  a  system  defeat  would  be  assured  before  the 
first  gun  was  fired. 


Art  of  War  Applied  to  Coast  Defence,  9 

From  this  point  of  view  it  is  evident  that  in  se-  *^ 
lee  ting  the  positions  on  our  sea- coast  to  be  perma- 
nently defended,  we  must  have  regard  not  only  to 
security  for  our  navy-yards  and  depots,  for  our 
great  fleet,  of  coastwise  trading  vessels,  for  our  im- 
portant cities — in  a  word,  for  the  points  which  a 
hostile  fleet  bent  on  scourging  us  into  accepting 
peace  by  inflicting  pecuniary  damages  would  select 
for  attack — but  also  to  providing  safe  rendezvous  for 
our  fleets  whence  they  can  sally  at  will  to  assume 
the  offensive. 

The  necessity  of  leaving  our  fleets  free  to  carry,  so 
to  speak,  the  war  into  the  enemy's  country  whenever 
occasion  offers,  is  no  new  theory  resulting  from  the 
peculiar  conditions  of  sea-coast  defence  to-day.  The 
idea  was  urged  in  the  Senate  by  Mr.  Webster,  with 
his  usual  eloquence,  in  1838  ;  and  was  so  well  ex- 
pressed by  Admiral  Dupont  in  1851  that  I  cannot  do 
better  than  quote  his  exact  language.    He  wrote  : 

"  I  beg  leave  to  express  an  emj^hatic  dissent  from 
all  theories  having  for  their  object  the  substitution 
of  active  ships  of  war  for  permanent  works.  This 
would  be  placing  the  Navy  in  a  false  position  before 
the  country  ;  giving  it  duties  to  x)erform  for  which 
its  organization  is  inapplicable  ;  preparing  for  its 
future  discredit  and  loss,  through  failures  to  execute 
that  which  should  never  have  been  undertaken, 
which  is  not  embraced  in  the  general  scope  and  de- 
sign of  a  naval  establishment. 

''To  retain  the  Navy  for  harbor  defence  was  en- 
tertained at  the  commencement  of  the  last  war  with 
England ;  the  proposition  to  do  so  sx3rung  from  the 
apprehension  that  it  could  not  compete  with  the 
vastly  superior  English  force  upon  the  ocean.  But 
at  that  time  some  brave  and  sagacious  officers  in  the 
high  ranks  saved  the  Navy  from  the  fate  that  threat- 
ened it,  and  to  these  gentlemen  it  owes  all  its  sub- 


10  General  Considerations. 

sequent  honors,  usefulness,  and  prosperity.  If  any 
such  ideas  prevail  at  this  day,  in  or  out  of  the  ^yo- 
fession,  those  holding  them  would  do  well  to  pause 
and  consider  wliat  the  Navy  would  have  lost,  and 
what  the  country  would  have  lost,  if  our  ships  of  war 
had  at  that  eventful  period  been  deprived  of  the  op- 
portunity of  filling  so  bright  a  page  in  the  Nation's 
history  by  their  achievements  ui)on  the  ocean." 

These  opinions  as  to  the  true  strategic  functions  of 
the  Navy  are  now,  it  is  believed,  generally  accepted, 
and  plans  for  coast  defence  should  be  so  arranged  as 
to  give  them  full  effect  wherever  possible  ;  ^.e.,  any 
complete  system  must  be  planned  to  furnish  safe 
bases  along  the  coast  from  which  offensive  operations 
can  be  undertaken  and  in  which  security  may  be 
found  in  the  event  of  disaster. 

This  matter  was  carefully  considered  by  the  Endi- 
cott  Board  of  1886,  and  provision  was  made  for  such 
rendezvous  at  Portland,  at  Boston,  at  Narragansett 
Bay,  at  New  York,  at  the  Delaware,  at  Hampton 
Roads,  at  the  mouth  of  the  Mississippi,  and  at  San 
Francisco  ;  /.e.,  at  eight  of  the  eleven  ports  at  which 
fortifications  were  reported  as  ''most  urgently  re- 
quired." Great  Britain  has  already  prepared  two 
such  rendezvous  in  our  waters  for  her  own  use — one 
at  Halifax  and  one  at  Bermuda  ;  and  rumor  reports 
that  she  has  another  in  view  in  the  near  future  at 
Victoria. 

Strategic  considerations  of  a  special  character  are 
suggested  in  connection  with  Portland  Harbor  ;  they 
give  it  a  prominence  to  which  the  wealth  and  import- 
ance of  the  city  itself  could  advance  no  claim.  It  is 
the  terminus  of  the  Grand  Trunk  Railroad  and  the 
natural  winter  outlet  of  the  Dominion  of  Canada. 
Its  importance  is  iDerfectly  appreciated  by  Great 
Britain.  Colonel  Strang,  R.A.,  in  a  lecture  before 
the  Royal  United  Service  Institution  in  1879  used  the 


Art  of  War  Applied  to  Coast  Defence.  11 

following  language  :  ^'Without  the  Canadian  Pacific 
Canada  is  a  cul-de-sac.  The  struggling  nationality- 
resembles  a  young  giant  whose  careless  parents  al- 
lowed one  nostril  to  be  stuffed  up  by  the  loss  of  the 
unfrozen  seaports  of  the  State  of  Maine  ;  and  now,, 
after  giving  up  Oregon  and  the  San  Juan  passage, 
that  other  Canadian  nostril,  we  are  threatened  with 
the  secession  of  British  Columbia,  which  can  neither 
be  defended  nor  traded  with.  .  .  .  Fortunately  at 
Halifax  we  have  retained  some  of  the  ultimce  rationed 
regum  et populorum.  We  need  not,  therefore,  discuss 
the  defence  of  this  fortress  and  harbor,  which,  how- 
ever valuable  in  other  senses,  can  in  no  sense  be 
considered  a  safe  base  for  operating  in  the  inland 
defence  of  Canada  ;  for  the  treaty  of  1842,  which 
handed  over  the  State  of  Maine,  sends  a  wedge  of 
territory  up  to  within  a  few  miles  of  the  inter- colo- 
nial railroad  which  a  handful  of  troopers  could  at 
any  moment  render  unserviceable  in  a  night,  thus 
cutting  off  retreat  to  Halifax  or  succor  from  thence 
to  the  upper  provinces.  It  is  true  that  detachments 
were  sent  from  Halifax  during  the  Trent  diiSculty  ; 
but  the  United  States  were  at  that  time  disunited 
States." 

The  value  of  Portland  as  a  temporary  British 
naval  station  during  a  war  with  the  United  States 
would  be  sure  to  attract  attention  ;  and  if,  in  case  of 
heavy  American  reverses,  our  opponent  should  be  in 
a  position  to  demand  a  land  indemnity  as  one  of  the 
conditions  of  peace,  as  did  Germany  in  the  late  war 
with  France — to  whom  the  idea  doubtless  seemed  as 
preposterous  at  the  outset  as  it  does  to  us  to-day — 
probably  no  section  of  the  country  would  be  so  likely 
to  be  desired  as  this  magnificent  port.  For  this  rea- 
son it  behooves  us  to  hold  it  strongly  against  any 
possible  attack.  If  Metz  and  Strasbourg  had  been 
unoccupied  by  a  German  army  when  fehe  terms  of 


12  General  Considerations. 

peace  were  agreed  upon,   they  might  have  escax)ed 
their  fate. 

The  strategic  importance  of  Boston  in  a  naval  war 
is  self-evident.  A  small  force  here  would  cover  the 
entire  coast  from  Cape  Cod  to  New  Brunswick 
against  marauding  expeditions  detached  from  a 
fleet  operating  against  New  York.  It  forms  the 
natural  base  for  fitting  out  offensive  operations 
against  Halifax  and  the  St.  Lawrence.  Lastly,  when 
properly  defended,  it  would  afford  refuge  to  the  whole 
fleet  of  New  England  fishing  and  coasting  vessels. 

Narragansett  Bay  covers  the  entrance  to  Long 
Island  Sound  and  all  the  small  harbors  on  its  shores. 
An  enemy  passing  Montauk  Point  would  leave  his 
communications  at  the  mercy  of  a  much  smaller  fleet 
lying  here  behind  land  defences  affording  security 
against  direct  attack.  Gardiner's  Bay,  at  the  east- 
ern end  of  Long  Island,  would  be  perhaps  a  better 
position ;  but  it  is  not  so  easily  defended  by  forts, 
and  it  lacks  the  importance  of  Narragansett  Bay  in 
other  respects.  Admiral  Simpson,  in  whose  profes- 
sional judgment  I  have  great  confidence,  has  always 
urged  the  importance  of  a  large  naval  establishment 
at  New  London,  not  only  from  its  natural  advan- 
tages, but  also  from  its  strategic  relations  to  Long 
Island  Sound.  Should  such  an  establishment  ever 
be  created  there,  the'  local  question  of  its  land  de- 
fences would  be  simple. 

The  supreme  importance  of  New  York,  the  com- 
mercial metropolis  of  our  Atlantic  seaboard,  is  un- 
questioned. No  demonstration  is  needed  either  as 
to  the  necessity  of  local  defence  or  as  to  the  facilities 
the  port  offers  for  offensive  sallies  in  every  direction. 

Hampton  Roads  bear  to  Chesapeake  Bay  a  rela- 
tion similar  to  that  of  Narragansett  Bay  to  Long 
Island  Sound.  A  small  force  driven  from  the  ocean 
by  a  superior  fleet  could  take  refuge  behind  a  forti- 


Art  of  War  Applied  to  Coast  Defence.         13 

lied  line  based  on  Fortress  Monroe,  and  from  this 
secure  position  could  threaten  the  passage  between 
the  Capes  so  effectually  that  no  enemy  could  afford 
to  operate  against  Baltimore  or  Washington  without 
leaving  behind  at  least  an  equal  detachment  to  cover 
his  only  route  of  communication  witli  the  ocean. 

The  lleet  charged  with  the  general  defence  of  the 
Gulf  Coast  would  find  its  principal  base  on  the  Mis- 
sissippi ;  where,  stationed  centrally,  it  could  operate 
at  any  point  between  the  Capes  of  Florida  and  the 
Rio  Grande  so  soon  as  the  telegra|)h  made  the  ap- 
proach of  the  marauders  known.  It  goes  without 
saying  that,  in  case  of  a  war  with  Spain,  Key  West 
would  become  a  place  of  great  strategic  importance 
by  reason  of  its  vicinity  to  Cuba,  and  the  facilities 
it  offers  as  a  base  for  land  operations  against  that 
island  and  for  blockading  its  coasts.  Controlling 
as  it  does  the  narrow  channel  leading  from  the  South 
Atlantic  Coast  to  the  Gulf  of  Mexico,  it  must  be 
firmly  held  in  any  maritime  war,  and  especially  in 
one  with  France  or  Great  Britain,  which  have  pos- 
sessions in  the  West  Indies. 

The  relations  of  San  Francisco  to  the  Pacific 
Coast  are  similar  to  those  of  New  Orleans  to  the 
Gulf  of  Mexico  ;  and  in  addition  it  would  be  our  base 
for  any  offensive  operations  on  the  Pacific,  at  least 
until  a  new  fortified  position  at  Puget  Sound  is  de- 
manded by  the  growth  of  population  in  that  direc- 
tion. 

These  views  as  to  the  strategic  points  along  our 
seaboard  are  based  upon  three  beliefs  :  (1)  that  it 
will  be  long  before  we  shall  have  a  Navy  strong 
enough  to  carry  the  war  across  the  Atlantic  and  thus 
keep  the  enemy  at  home  ;  (2)  that  present  indications 
of  awakened  interest  warrant  the  opinion  that  we 
shall  soon  have  a  Navy  which,  if  afforded  secure 
points  of  refuge,  would  by  frequent  sallies  make  its 


14  General  Considerations , 

influence  felt  against  an  attacking  fleet  too  strong  to 
be  faced  in  a  pitched  battle,  thus  extending  indirect 
protection  to  the  small  ports  along  our  entire  sea- 
coast  ;  and  (3)  that  if  we  neglect  to  prepare  these 
places  of  refuge,  our  new  Navy  may  be  swept  from 
the  ocean,  as  was  the  Huascar^  or  may  be  ignomi- 
niously  captured  in  our  harbors,  as  happened  to  the 
Danube  squadron  in  the  late  Russo-Turkish  war, 
and  as  has  happened  to  fleets  again  and  again  in 
days  gone  by. 

If  we  should  fritter  away  our  resources  in  con- 
structing armored  ships  with  a  view  to  chaining 
them  in  harbors  where  local  conditions  make  a  land 
defence  more  economical — and  this  statement  is  true 
for  all  our  ports  except  San  Francisco  and  the  mouth 
of  the  Mississippi — we  should  not  only  waste  money 
but  should  also  create  a  Navy  ill-suited  to  perform 
the  duties  which  sound  strategic  principles  demand 
of  that  arm  of  the  service.  In  my  judgment,  the 
Navy,  like  cavalry,  loses  half  its  power  if  not  threat- 
ening the  offensive. 

I  make  no  reference  to  the  strategic  use  of  tor- 
pedo-boat flotillas,  because  I  am  not  sufiiciently  in- 
formed as  to  their  ability  to  keep  the  sea  in  tempes- 
tuous weather,  concerning  which  there  appears  to  be 
some  difference  of  opinion  since  the  recent  French 
evolutions.  Of  one  thing,  however,  I  am  sure. 
These  boats  will  play  a  very  imi)ortant  part  in  con- 
nection with  our  projected  land  defences,  as  will  be 
more  fully  elaborated  hereafter. 

Grand  Tactics. — Grand  tactics  treat  of  the  art 
of  well  combining  and  well  conducting  battles.  In 
the  shock  of  armies  manoeuvring  for  position  much 
is  necessarily  left  to  chance,  because  neither  com- 
batant is  possessed  of  the  plans  and  views  of  his  op- 
ponent, and  accident  or  lack  of  time  may  compel  the 
neglect  of    well- recognized  rules.     A  seaport  to  be 


Art  of  War  Applied  to  Coast  Defence.         15 

fortified  sliould  be  carefully  studied  in  advance,  and 
with  ample  time  and  means  no  such  mistakes  are 
justifiable. 

On  land  the  weak  positions  of  a  line  of  battle  are 
usually  the  flanks  ;  and  if  the  line  be  too  strong  and 
well  occupied  for  a  front  attack,  the  assailant  usually 
manoeuvres  to  turn  one  of  them.  But  when  the 
enemy  is  confined  to  his  ships  he  can  move  only  by 
navigable  channels  ;  we  may  with  certainty  foresee 
what,  if  any,  flank  ox)erations  will  be  practicable, 
and  by  preparing  to  meet  them  may  compel  him  to 
either  attack  where  we  have  carefully  prepared  a 
battle-field  .to  give  us  every  advantage,  or,  as  has 
often  happened,  to  abandon  his  intention  of  attack- 
ing. This  latter  sliould  he  the  aim  of  the  Engineer 
in  fortifying  a  harhor^  for  it  is  an  accepted  principle 
never  to  seek  a  battle  unless  the  chances  of  advan- 
tage which  will  accrue  in  case  of  success  shall  pre- 
ponderate over  the  chances  of  loss  if  defeated  ;  and 
this  condition  can  rarely  if  ever  be  fulfilled  in  a  bat- 
tle fought  to  prevent  the  occupation  of  an  important 
harhor  by  a  hostile  fleet. 

The  maxims  of  grand  tactics  applicable  to  coast 
defence  teach  us  the  following :  (1)  to  provide  for  of- 
fensive movements  of  our  own  torpedo-boats,  and  of 
our  armored  ships  if  any  be  present.  This  princi- 
ple forbids  the  closure  of  channels  by  obstructions 
which  cannot  be  passed  by  our  own  vessels  ;  (2)  to  so 
place  our  land  guns  as  to  assure  their  mutual  sup- 
port and  their  most  effective  service  against  the 
enemy.  Mutual  support  is  important  to  prevent  the 
overwhelming  of  one  battery  by  the  concentration  of 
superior  fire,  which  is  always  to  be  expected  in  a 
deliberate  attack.  In  discussing  the  defences  of 
Spezzia  the  Italian  engineers  laid  great  stress  upon 
this  point ;  and  a  position  which  would  permit  an 
enemy  to    bombard  the  docks  and  navy-yard  at  a 


16  General  Considerations . 

range  of  only  4.6  miles  was  advocated,  and  I  think 
has  been  adopted,  rather  than  secure  a  longer  range 
at  the  expense  of  exposing  isolated  turrets  to  a  con- 
centric fire  ;  (3)  to  guard  well  the  flanks  by  closing 
all  unnecessary  channels,  and  thus  compel  the  enemy 
to  make  a  direct  attack  or  to  make  none  at  all — the 
application  of  this  principle  has  been  already  con- 
sidered ;  (4)  to  provide  means  for  offensive  returns 
against  countermining  oj)erations  in  the  absence  of 
torpedo-boats  of  our  own.  This  is  the  true  function 
of  movable  torpedoes  operated  and  directed  from  the 
shore.  A  purely  passive  defence,  whether  on  land  or 
sea,  is  rarely  successful. 

Logistics. — This  branch  of  the  art  of  war  is  con- 
cerned with  the  preparation  in  advance,  with  the  pro- 
per storage,  and  with  the  transportation  of  all  ma- 
terial needful  for  use  in  connection  with  the  opera- 
tions of  an  army.  In  sea-coast  fortification  it  has  to 
do  with  supplies  of  all  kinds,  and  with  preparations 
to  receive  and  store  them.  Thus  magazines  and 
shell-rooms  ample  to  contain  the  immense  quantities 
of  ammunition  demanded  by  modern  guns,  and,  yet 
absolutely  bomb-proof,  are  a  necessity.  Bomb-proof 
cover  for  the  garrison,  the  stores,  and  the  military 
material ;  safe  covered  passages  for  the  movement  of 
ammunition  in  action  ;  protected  routes  for  introduc 
ing  the  electric  cables  of  the  submarine  mines  ;  and 
many  other  matters  too  numerous  to  mention,  per- 
taining to  the  domain  of  logistics,  press  upon  the 
attention  of  the  military  engineer.  The  Navy  has 
troubles  of  its  own  of  a  like  character ;  but  I  think 
neither  branch  of  the  service  has  much  to  learn  from 
a  study  of  rules  in  logistics  evolved  from  the  expe- 
rience of  armies  in  the  field. 

The  Art  of  the  Engineer. — This  branch  of  the 
art  of  war,  which  as  applied  to  coast  defence  includes 
locating,    planning,   and  constructing   the    fortifica- 


Art  of  War  Applied  to  Coast  Defence.  17 

tions,  largely  forms  the  subject  of  these  lectures.  It 
calls  for  an  appreciation  of  the  power  and  of  the 
weakness  of  modern  ships  of  war,  of  modern  ord- 
nance and  torjDedoes,  and,  in  general,  of  the  most 
effective  and  economical  methods  of  securing  every 
possible  advantage  to  the  defence  by  applying  such 
means  as  are  available.  Each  element  must  be  con- 
sidered and  weighed  as  to  its  relative  cost  and  rela- 
tive efficiency.  The  funds  allotted  to  sea-coast  de- 
fences by  all  nations  are  limited,  and  what  is  wasted 
in  injudicious  expenditure  will  certainly  be  sub- 
tracted from  some  needful  outlay.  For  example, 
nothing  could  be  easier  than  to  make  an  impregnable 
fort  if  cost  were  left  out  of  consideration.  Armor- 
plates,  whether  steel,  or  compound,  or  wrought  iron, 
or  chilled  cast  iron,  can  be  made  thick  enough  to 
keep  out  the  projectiles  of  any  gun  now  existing  or 
which  ever  can  exist.  If  three  feet  of  armor  will  not 
do  it,  ten  feet  will.  There  is  no  limit  to  the  secu- 
rity attainable  in  a  land  battery,  where  any  weight 
whatever  can  be  supported.  But  the  skill  of  the 
engineer  lies  in  a  judicious  estimate  of  what  is  need- 
ful and  of  what  is  superfluous,  and  in  making  his 
plans  and  applying  his  funds  accordingly. 

This  principle  has  always  governed  the  Engineer 
Department.  By  skilfully  applying  it  to  a  problem 
all  the  elements  of  which  were  then  known  and  ad- 
mitted of  computation.  General  Totten  was  able  to 
give  to  the  country  what  at  their  date  were  perhaps 
the  most  perfect  sea-coast  fortifications  the  world  has 
ever  seen,  and  to  accomplish  the  task  with  funds 
which  Congress  was  willing  to  grant. 

But  this  is  the  age  of  progress.  The  introduction 
of  the  screw-propeller  led  to  the  use  of  guns  throw- 
ing shells  which  no  ships  could  endure,  and  hence 
to  the  introduction  of  armor.  Then  followed  the  long 
struggle  for  supremacy  between  ordnance  and  armor, 


18  General  Considerations. 

which  unsettled  all  ideas  and  made  the  problem  one 
rather  of  prophecy  thali  of  knowledge.  This  was  the 
condition  at  the  close  of  the  civil  war.  It  was  the 
judgment  of  the  best  officers  of  the  Corps  of  En- 
gineers, shared  and  carried  into  effect  by  Gfeneral 
Humphreys,  that  the  time  was  ill-suited  for  the  selec- 
tion of  a  permanent  system  ;  but  that  all  funds  avail- 
able could  be  wisely  applied  to  inaugurating  a  system 
of  earth- works  which  would  meet  the  needs  of  the 
moment  and  would  remain  useful  when  a  more  defi- 
nite estimate  of  what  could  be  accomplished  in  ar- 
mored ships  and  ordnance  was  possible. 

This  time  has  now  come — at  least  as  to  the  essen- 
tial elements — and  it  is  my  purpose  in  these  lectures 
to  consider  each  point  in  sufficient  detail  to  give  a 
fair  idea  of  the  proposed  system,  from  the  point  of 
view  of  a  military  engineer. 

It  should  be  understood  at  the  outset  that  the  de- 
fence of  each  important  locality  forms  a  study  in  it- 
self. Nature  has  nowhere  given  us  sites  combining 
every  desirable  feature.  The  Engineer  must  avail 
himself  of  every  natural  advantage  to  the  utmost, 
and  must  deal  with  natural  defects  in  such  a  manner 
as  to  secure  the  maximum  of  strength  at  the  mini- 
mum of  cost. 

This  mode  of  approaching  the  subject  reveals  the 
base  metal  of  which  many  theories  of  defence  are 
constructed.  One  savant  informs  us  that  inexpensive 
submarine  mines,  easily  improvised,  are  sufficient  to 
close  any  harbor  ;  another  proposes  movable  torpe- 
does under  control  from  the  shore,  or  from  armored 
rafts  at  anchor,  as  the  needful  panacea ;  another 
simply  advocates  a  line  of  turrets,  armed  with  mod- 
ern high-power  guns ;  another  finds  a  perfect  de- 
fence in  a  few  disappearing  guns  fired  from  pits  ; 
another  would  trust  to  a  swarm  of  torpedo-boats  of 
the  approved   type ;  while  another  pins  his   faith 


Art  of  War  Applied  to  Coast  Defence.         19 

solely  upon  a  fleet  of  armored  ships  of  war.  The 
truth  is,  such  crude  assertions,  stamp  the  utterer  as 
a  military  quack.  All  of  these  devices,  and  others, 
find  useful  applications  ;  but  as  soon  as  a  serious 
study  of  our  harbors  is  made  it  becomes  apparent 
that  there  are  locations  where,  so  far  from  being  suf- 
ficient, each  of  them  in  turn  is  quite  inapplicable. 
There  is  no  medicine  which  will  cure  all  the  ills  to 
which  flesh  is  heir  ;  and  the  same  is  eminently  true 
of  an  exposed  sea-coast.  To-day  a  satisfactory  solu- 
tion can  in  general  be  secured  only  by  a  complex 
combination  of  many  elements,  varying  according  to 
locality  to  an  extent  which  forbids  any  summary  not 
•couched  in  the  most  comprehensive  terms.  Each 
individual  case  must  be  discussed  on  its  own 
merits. 

In  general,  an  important  seaport  well  defended 
implies  :  (1)  the  effective  obstruction  of  all  water  ap- 
proaches against  the  enemy,  leaving  free  entrance 
and  exit  for  our  own  vessels  ;  (2)  protection  for  these 
•obstructions,  and  security  for  their  operators  and 
their  flanking  guns  against  escalade  by  boat  parties  ; 
{3)  so  heavy  a  fire  of  modern  high-power  guns  and 
mortars  over  all  the  approaches  as  to  defy  the  most 
powerful  armored  fleet  able  to  operate  in  the  chan- 
nels leading  to  these  auxiliary  defences  ;  (4)  a  heavy 
flanking  flre  of  medium  and  small  projectiles  over 
the  obstructed  zone;  (5)  provision  for  offensive  re- 
turns against  armored  counterminers  ;  (6)  the  power 
■of  illuminating  the  obstructions  by  night,  so  far  as 
this  is  physically  possible ;  (7)  a  swarm  of  torpedo- 
Iboats  which,  safe  behind  the  barrier,  are  always 
ready  to  sally  out  and  carry  the  war  to  the  enemy's 
fleet  when  favorable  opportunities  occur. 

Harbors  of  minor  importance  may  be  sufficiently 
-def ended  upon  less  elaborate  systems ;  but  at  the 
ports  which  the  Fortification  Board  of  1886  reported 


20  General  Considerations. 

as  "  most  urgently  requiring  defences"  it  would  be 
criminal  to  neglect  any  of  those  named. 

The  first  matters  for  consideration  in  deciding 
how  any  particular  position  shall  be  fortified  are  the 
calibres  and  numbers  of  the  heavy  guns  needful  to 
overpower  the  enemy's  fire.  These  will  be  determin- 
ed in  accordance  with  our  estimate  of  what  he  can 
bring  to  the  attack,  and  what  tactics  will  probably  be 
adopted  in  making  it. 

I  naturally  feel  some  difladence  in  discussing  this 
branch  of  my  subject  before  Naval  experts  ;  but  as 
the  question  is  a  vital  one  for  Army  engineers,  I 
shall  undertake  the  task,  hoping  to  receive  candid 
criticism  as  to  any  points  concerning  which  my  con- 
clusions may  appear  to  be  at  fault. 

PEOBABLE  NATURE  OF  THE  ATTACK. 

The  calibre  of  the  land  guns  must  be  sufficient  to 
pierce  the  armor  of  the  enemy  at  a  two-mile  range, 
and  to  compete  with  his  artillery  on  at  least  equal 
terms.  His  possible  armament  and  armor  are  both 
fixed  by  the  available  depth  of  water  in  the  channel 
of  approach.  Since  the  guns  of  most  modern  ships 
will  pierce  the  armor  they  carry  at  considerable 
ranges,  a  rough  estimate  of  what  calibres  we  should 
provide  may  be  formed  by  studying  the  armament  of 
modern  ships  in  connection  with  their  draught  and 
the  depth  of   water  in  the  channel  to  be  defended. 

Needful  Calibres. — Thus,  taking  the  British 
Navy  as  an  example,  the  Benhow,  Renown,  and  Sans- 
pareil  each  carry  two  110- ton  B.  L.  guns,  with  from 
ten  to  thirteen  6-inch  or  larger  high-power  guns. 
They  all  draw  27  feet.  No  vessel  with  a  less  draught 
is  now  armed  with  110- ton  guns.  The  ColUngwood, 
Conqueror,  Hero,  Colossus,  and  Edinburgli  each, 
carry  either  four  or  two   12-incli  43-ton   guns,  with 


Probable  Nature  of  the  Attack,  21 

four,  five,  or  six  high-power  6-inch  guns ;  and  the 
Inflexible^  four  16-inch  80-ton  guns.  Their  draught 
ranges  from  24  feet  to  26  feet.  The  belted  cruisers 
Orlando^  Undaunted,,  Australia,,  Narcissus^  and 
Galatea  each  carry  two  9.2-inch  18- ton  guns,  and  ten 
high-power  6-inch  guns.  Their  draught  is  22>^  feet. 
As  a  rule  no  armored  ships  draw  less  than  20  feet, 
except  the  so-called  Coast  Defenders,  which  draw 
about  18  feet ;  but  unarmored  cruisers  drawing  only 
16  feet  could,  in  the  present  condition  of  our  sea- 
coast  armament,  work  great  destruction  at  ranges 
where  our  gtins  would  be  powerless  to  reply.  This 
class  carries  about  10  guns,  varying  between  9  inches 
and  6  inches  in  calibre  ;  and  a  swarm  of  gunboats 
drawing  less  than  16  feet  carry  muzzle-loading  10- 
inch  18-ton  guns. 

No  discussion  of  the  power  of  these  guns  is  need- 
ful here  ;  I  will  only  recall  that  their  muzzle  energies 
are  approximately  as  follows  : 

That  of  the  16j<-inch  llO-ton  B.  L.  gun  is  57  000 
foot-tons. 

That  of  the  16-inch  80-lon  M.  L.  gun  is  30  000 
foot-tons. 

That  of  the  12-inch  46-ton  B.  L.  gun  is  24  000 
foot-tons. 

That  of  the  12-inch  43-ton  B.  L.  gun  is  15  000 
foot-tons. 

That  of  the  9.2-inch  18-ton  B.  L.  gun  is  9  000  foot- 
tons. 

That  of  the  10-inch  18-ton  M.  L.  gun  is  5  000  foot- 
tons. 

That  bf  the  6-inch  4-ton  B.  L.  gun  is  2  500  foot- 
tons. 

The  estimate  to  be  placed  upon  the  offensive 
power  of  these  guns  will  of  course  depend  upon  the- 
nature  of  the  proposed  works  ;  for  example,  a  6-inch 
gun,  little  to  be  feared  by  a  turret  or  an  armored 


u 


22  General  Considerations. 

casemate,  might  by  its  rapidity  of  fire  be  more  for- 
midable against  an  exposed  barbette  than  even  a  100- 
ton  gun.  In  such  cases  shrapnel-fire  becomes  spe- 
cially dangerous.  Its  effect  is  terrible,  provided  the 
projectile  be  exploded  at  exactly  the  right  place ; 
fortunately  for  open  barbettes,  precision  of  fire  is 
diflBcult  to  secure  on  shipboard,  and  no  perfect  time- 
fuse exists. 

Another  element  of  the  armament  of  modern  ships 
must  not  be  forgotten — the  rapid-firing  and  machine 
guns.  Their  record  at  Alexandria  was  a  poor  one, 
but  improvements  are  constantly  making  and  they 
will  certainly  be  brought  against  forts.  The  best  de- 
fence is  shoal  v^ater  or  submarine  mines,  which  for- 
bid approach  within  a  thousand  or  twelve  hundred 
yards'  range ;  but  wlien  it  is  not  possible  to  secure 
this  advantage,  guns  on  low  sites,  without  cover  dur- 
ing loading,  must  be  regarded  as  of  little  value. 

After  studying  the  map  of  the  entrance  to  be  de- 
fended, in  connection  with  lists  of  war-ships,  which 
for  all  navies  are  easily  accessible,  the  engineer  can 
form  a  fair  estimate  of  the  calibres  of  the  guns  likely 
to  be  brought  against  him.  Two  points  should  not 
be  forgotten :  (1)  Coast  Defenders  of  comparatively 
little  draught  can  carry  the  largest  modern  guns,  and, 
although  they  would  not  be  allowed  to  leave  their 
regular  posts  of  duty  in  a  war  with  a  formidable 
maritime  power,  they  may  be  expected  on  our  shores 
for  many  years  to  come  ;  and  (2)  the  moral  effect  of  a 
few  land  guns  of  larger  calibre  than  any  carried  by 
the  fleet  is  very  great.  The  influence  of  General  Tot- 
ten  was  powerfully  exerted  to  secure  the  introduction 
of  the  15-inch  S.  B.  gun  when  that  was  supposed  to 
be  quite  beyond  the  ability  of  ships  to  carry ;  the 
^'largest  gun  possible"  is  a  time-honored  maxim 
with  us,  and  I  think  the  projects  of  the  Corps  of  En- 
gineers for  our  chief  harbors  will  always  provide  for 


Probable  Nature  of  the  Attack.  23 

a  few  of  tlie  most  powerful  guns  which  the  genius  of 
the  age  can  fabricate  successfully. 

As  stated  above,  our  largest  guns  should  at  least 
be  able  to  pierce  the  armor  of  the  enemy  at  a  two- 
mile  range.  This  limit  is  adopted,  partly  because 
ships  must  approach  to  that  distance  to  seriously  an- 
noy land  guns  properly  mounted;  partly  because,  with 
ships  and  forts  more  or  less  shrouded  in  smoke,  pre- 
cision of  fire  on  our  part  is  not  to  be  expected  at 
longer  ranges  ;.  and  partly  because  the  area  of  the 
ship  protected  by  her  heaviest  armor  forms  but  a 
small  per  cent,  of  that  exposed  to  our  blows,  and  she 
may  receive  great  injury  from  shots  powerless  to 
pierce  her  at  the  water-line. 

Number  of  Guns. — The  next  point  for  conside  - 
ration  is  the  number  of  the  guns  likely  to  be  brought 
against  the  port  under  study,  by  the  most  powerful 
enemy.  The  number  which  a  single  vessel  of  each 
class  carries  has  already  been  noted  ;  the  present 
question  is  therefore  restricted  to  the  local  problem 
of  how  many  ships  can  be  placed  in  position.  For 
ports  of  the  first  class  the  basis  of  the  estimate 
should  be  the  full  strength  of  possible  attack ;  for 
ports  of  minor  importance  the  Engineer  will  be  guid- 
ed by  his  judgment  as  to  the  size  of  the  fleet  likely  to 
be  detached  for  the  purpose. 

The  determination  of  the  length  of  the  front  of 
attack  is  a  simple  matter  of  map  and  dividers.  Draw 
circles  with  radii  varying  from  one  to  three  miles, 
the  centre  being  the  fort  under  consideration,  and 
note  the  lengths  which  fall  upon  water  of  sufficient 
depth  and  otherwise  suitable  for  occupation  by  war- 
ships. The  probable  distance  and  the  maximum  de- 
velopment of  the  attack  can  thus  be  estimated  with 
precision. 

How  near  together  the  ships  can  be  safely  manoeu- 
vred will  depend  upon  the  strength  of  the  current 


24  General  Considerations. 

and  the  nature  of  the  channel,  whether  clear  or  ob- 
structed by  shoals,  reefs,  or  suspected  torpedoes. 
At  Alexandria,  where  there  was  no  need  of  crowding, 
about  four  ships  occupied  one  mile.  At  Charleston, 
on  April  7,  1863,  the  monitors  in  a  difficult  channel 
formed  at  intervals  of  "one  cable  length,"  or  at  the 
rate  of  about  eight  monitors  per  mile.  At  the  attack 
on  Fort  Fisher  on  December  24-25,  1864,  as  well  as 
that  of  January  13,  1865,  the  favorable  position  and 
calm  weather  offered  exceptionally  advantageous 
conditions  to  the  fleet.  The  monitors  were  ordered 
to  be  anchored  '^not  more  than  one  length  apart." 
The  diagram  accompanying  Admiral  Porter's  official 
report  of  the  final  attack  indicates  that  the  first  line 
(14  vessels)  occupied  a  development  of  three-quarters 
of  a  mile  ;  the  second  line  (12  vessels)  a  development 
of  three-quarters  of  a  mile ;  and  the  third  line  (14 
vessels)  a  development  of  one  mile.  The  diagram  of 
the  December  attack  (which  formed  part  of  the  offi- 
cial order  for  the  engagement)  does  not  materially 
differ  in  respect  to  length  of  development.  The  Ad- 
miral evidently  designed  to  deploy  his  vessels  at  the 
rate  of  about  fifteen  to  the  mile. 

These  facts,  I  think,  warrant  the  conclusion  that 
the  larger  ships  of  war  of  to-day,  under  the  most 
favorable  conditions,  may  be  expected  to  deploy  in  a 
single  line  at  the  rate  of  about  ten  to  the  mile,  but 
that  in  a  contracted  and  unfavorable  channel  not 
more  than  five  of  them  would  be  likely  to  make  the 
attempt.  Indeed,  some  individual  vessels  are  claimed 
to  require  a  mile  in  which  to  manoeuvre  with  safety  to 
their  neighbors.  In  fine,  my  studies  induce  the  be- 
lief that,  allowing  to  each  vessel  six  effective  guns  of 
calibres  varying  from  six  inches  upwards,  according 
to  her  draught,  we  must  anticipate  a  possible  fire  at 
the  rate  of  thirty  to  sixty  guns  j)er  mile  of  available 
development,  depending  upon  the  nature  of  the  site. 


Prohahle  Nature  of  the  Attack.  25 

The  next  point  for  consideration  is  the  old  and 
much-mooted  question  of  relative  efficiency  between 
land  guns  and  those  mounted  on  shipboard.  This 
question  is  open  to  intelligent  differences  of  opinion, 
but,  as  the  Engineer  must  commit  himself  to  some 
definite  estimate  upon  which  to  regulate  the  aTma- 
ment,  I  will  state  my  own  opinion,  with  some  of  the 
grounds  upon  which  it  is  based. 

Guns  Ashore  and  Guns  Afloat. — Formerly  it 
was  a  maxim  accepted  by  French  engineers  that  one 
gun  on  shore  was  able,  when  properly  mounted  and 
served,  to  contend  successfully  with  from  eight  to 
thirty  on  shipboard.  This  rule,  derived  from  expe- 
rience in  such  contests  in  olden  times,  was  verified 
in  the  naval  attack  on  Sebastopol,  where  ''an  earth- 
en battery  mounting  only  five  guns,  but  placed  on 
the  cliff  at  an  elevation  of  100  feet,  inflicted  grievous 
injury  on  four  powerful  English  ships  of  war,  and 
actually  disabled  two  of  them,  without  itself  having  a 
gun  dismounted  and  without  losing  even  one  man." 
But  the  rule  was  founded  on  conditions  no  longer 
existing.  The  ship  guns  of  that  period  were  small  in 
calibre ;  were  crowded  closely  together ;  were  cov- 
ered by  bulwarks  of  oak,  which,  when  struck  by  such 
projectiles  as  were  used  in  coast  batteries,  afforded 
little  j)rotection  ;  the  ship  was  soon  buried  in  smoke, 
which  prevented  the  scores  of  gunners  either  from 
seeing  how  to  aim  or  from  being  guided  with  any 
precision  by  orders  from  aloft ;  and,  lastly,  the  ar- 
mament was  not  readily  brought  to  bear  by  reason  of 
the  unwieldy  nature  of  the  ship,  which  floated  at 
the  mercy  of  baffling  winds  and  shifting  currents, 
with  her  masts  and  sails  exposed  to  destruction  by  a 
single  lucky  shot. 

A  modern  duel  between  ships  and  forts  is  fought 
under  very  different  conditions.  The  ships  are  more 
or  less   protected  by  armor  in  all  vital  parts;   the 


26  General  Considerations. 

motive  power,  deep  under  water  and  carefully  with- 
drawn, by  the  mode  of  manoeuvring,  from  direct  fire, 
is  comparatively  little  exposed  to  injury;  the  guns 
are  much  fewer  in  number,  and  the  smoke,  although 
still  a  serious  cause  of  inaccuracy  of  aim,  will  hardly 
form  the  impenetrable  veil  which  hung  about  the  old 
three- decker  in  action,  and  its  evil  effects  can  be 
more  easily  counteracted  ;  moreover,  the  reduced  size 
of  the  crews,  and  the  protective  armor  (if  the  latter 
be  sufficiently  substantial  for  its  work),  will  reduce 
casualties,  and,  leaving  torpedoes  out  of  the  ques- 
tion, the  hideous  carnage  of  old  naval  contests  will 
no  longer  appall  the  crew. 

'  On  the  other  hand,  it  must  not  be  forgotten  that 
the  risk  of  injury  when  struck  by  an  effective- 
modern  projectile  is  far  greater  for  the  ship  than  for 
the  land  battery.  The  latter  may  be  disfigured  by 
huge  craters  in  the  parapet,  a  few  men  may  be  killed, 
and  a  few  guns  may  be  dismounted,  but  so  long  as 
the  magazines  are  secure  no  overwhelming  disaster  is 
to  be  feared.  But  one  projectile  which  has  forced  its 
way  into  the  complex  mechanism  covered  by  the 
armor  plating  of  the  ship  may  annihilate,  at  a  single 
blow,  the  offensive  power  of  an  Italia^  of  an  Inflexi- 
ble^ or  of  a  Trafalgar.  Moreover,  the  shij)  fires  from 
an  unstable  deck,  at  varying  and  uncertain  distances, 
and  always  more  or  less  annoyed  by  the  smoke  of  her 
own  guns ;  the  land  battery,  aided  by  the  modern 
system  of  position-finding,  is  comparatively  unaffect- 
ed by  smoke  and  can  direct  its  fire  with  greater  pre- 
cision than  the  ship,  and  with  vastly  greater  certainty 
than  in  the  days  gone  by. 

One  question  formerly  stoutly  contested  has  been 
practically  answered  so  many  times  in  late  years  that 
there  is  no  longer  any  difference  of  opinion  upon  the 
subject :  every  one  now  admits  that  a  fleet  can  force 
a  passage  past  a  line  of  batteries  of  equal  or  even  of 


Probable  Nature  of  the  Attack.  27 

superior  armament,  provided  tlie  channel  be  unob- 
structed. Hence  in  studying  recent  experience  we 
may  leave  this  class  of  operations  entirely  out  of  con- 
sideration, and  confine  our  attention  exclusively  to 
instances  of  pitched  battles  between  armored  ships 
and  forts.  Combats  of  this  kind  are  inevitable  when 
the  channel  is  obstructed  by  mines  properly  .defend- 
ed ;  and  I  shall  ask  your  attention  to  a  few  instances 
which  throw  light  on  the  problem,  although  it  must 
be  admitted  that  experience  is  still  lacking  on  which 
to  formulate  definite  rules — if,  indeed,  it  will  ever  be 
possible  to  formulate  rules  where  so  great  variations 
exist  in  the  protection  afforded  by  different  types  of 
armored  ships  and  by  different  modes  of  mounting 
and  protecting  land  guns.  Still,  experience  is  the 
only  safe  guide,  and  use  should  be  made  of  all  that  is 
available. 

On  May  15,  1862,  an  earthen  battery  situated 
on  Drewry's  Bluff  about  100  feet  above  James  Ri- 
ver, and  without  bomb-proof  cover,  was  attacked 
by  two  iron-clads,  the  Galena  and  the  Monitor^  and 
by  three  wooden  vessels,  the  Aroostook^  the  Port 
Poyal,  and  the  JVaugattick.  The  iron  clads  anchored 
at  from  600  to  1  000  yards  range,  where  a  double  pile 
obstruction,  reinforced  by  hulks,  pre^^ented  a  nearer 
approach ;  the  wooden  vessels  anchored  about  1  300 
yards  below.  After  fighting  for  about  three  and  a 
quarter  hours  the  fleet  was  repulsed  ;  the  Galena  had 
expended  nearly  all  her  ammunition  and  had  suf- 
fered severely,  being  hulled  several  times.  The 
Monitor  and  apparently  the  wooden  vessels  were  not 
seriously  injured ;  but  Lieut. -Commander  Jeffers, 
commanding  the  Monitor,  reported  :  "So  long  as  our 
vessels  kept  up  a  rapid  fire  they  rarely  fired  in  re- 
turn, but  the  moment  our  fire  slackened  they  re- 
manned  their  guns.  It  was  impossible  to  reduce  such 
works,  except  by  the  aid  of  a  land  force." 


28  General  Coitsiderations. 

Tlie  armament  of  the  Galena  consisted  of  9-inch 
Dahlgreii  smooth-bores  and  Parrott  rifles  ;  the  Moni- 
tor carried  two  15-inch  guns  ;  the  armament  of  the 
wooden  vessels  is  not  stated  in  the  ofiicial  reports. 

When  Fort  Drewry  was  captured,  in  1865,  the 
water-bearing  guns  consisted  of  one  7-inch  Brooke 
rifle,  with  six  10-inch  and  three  8-inch  Rodman 
smooth-bores.  I  was  personally  informed  by  Major 
Drewry,  who  had  commanded  in  the  action  of  May 
15,  1862,  that  at  that  date  he  had  only  three  Rodman 
smooth-bores  in  position,  the  others  having  been 
added  subsequently. 

This  was,  I  believe,  the  first  decisive  contest  be 
.tween  our  armor-clad  vessels  and  a  land  battery. 
Although  the  result  was  a  disappointment,  and  the 
vessels  were  repulsed  with  loss  by  a  greatly  inferior 
force,  it  must  not  be  forgotten  that  the  trial  took 
place  under  conditions  which  gave  many  advantages 
to  the  land  forces — the  narrowness  of  the  river  even 
permitting  them  to  annoy  the  fleet  with  musketry. 

The  next  typical  pitched  battle  between  guns 
ashore  and  guns  afloat  took  place  at  Fort  Sumter  on 
April  7,  1863.  The  day  was  calm  and  all  the  con- 
ditions were  favorable  to  the  fleet. 

Fort  Sumter  at  that  date  consisted  of  an  un- 
finished masonry  work  having  a  single  tier  of  case- 
mates, strengthened  by  such  means  as  the  Con- 
federates had  found  practicable  after  its  occupation. 
The  masonry  was  largely  shell  concrete  faced  with 
brick ;  the  scarp  was  8  feet  thick  (5  feet  in  front 
of  the  recess  arch  and  11  feet  at  the  piers).  The  site 
was  a  small  artificial  island. 

The  armament  which  repulsed  the  attack  of  Ad- 
miral Dupont  was  mounted  in  Fort  Sumter,  Fort 
Moultrie,  and  in  the  batteries  on  Sullivan's  Island. 
The  Confederate  official  report  gives  the  following 
;statement  of  the  guns  and  mortars  used  in  the  battle : 


Prohahle  Nature  of  the  Attack.  29 

GUNS  AND  MORTARS  IN  USE  ON  APRIL  7,  1863. 


m 

m 

OD 

. 

rri 

ts 

J3 

•c 

.-  flj 

Fort  or  Battery. 

% 

CD 

« 

.2 

1 

so 

a 

IS 

s 

11 

1 

5 

3 

2 
I 

Fort  Sumter 

4 

2 

2 

8 

7 

1 

13 

7 

44 

Fort  Moultrie 

9 

5 

5 

2 

21 

Battery  Bee 

5 

1 

.. 

6 

Battery  Beauregard.. 

•• 

. . 

1 

1 

2 

Cumraiiigs  Point 

1 

1 

.. 

.. 

2 

Battery  Wagner 

•• 

•• 

1 

•• 

1 

Total 

10 

3 

2 

19 

7 

8 

18 

9 

76 

Fort  Sumter  fired  831  rounds ;  Fort  Moultrie,  868 
rounds  ;  Battery  Bee,  283  rounds  ;  Battery  Beaure- 
gard, 157  rounds  ;  Cummings  Point,  66  rounds  ;  Bat- 
tery Wagner,  22  rounds  ;  total,  2  227  rounds.  In  all 
21  093  pounds  of  powder  were  used. 

The  fleet  consisted  of  the  New  Ironsides^  the 
Keokuk^  and  seven  monitors.  Twenty-three  guns 
were  used  in  the  action :  seven  15-inch  Dahlgrens, 
fourteen  11-inch  Dahlgrens,  and  two  150-pounder  rifles. 
One  hundred  and  thirty-nine  shots  were  flred  by  the 
fleet  (124  of  them  at  Fort  Sumter).  The  15-inch  guns 
were  charged  with  35  pounds  of  powder,  the  11-inch 
guns  with  20  pounds,  and  the  150-pounders  with 
16  pounds. 

Admiral  Dupont  reported  the  range  of  the  moni- 
tors as  from  550  to  800  yards,  that  of  the  Ironsides 
being  not  less  than  1  000  yards  ;  his  ordnance  officer, 
Lieut.  A.  S.  Mackenzie,  reports  the  ranges  as  from 
550  to  2  100  yards  ;   tlie  Confederate  engineers  give 


30  General  Considerations. 

them   as  from   900   to  1 500  yards,   averaging  1  200 
yards. 

The  engagement  lasted  two  and  one-half  hours. 
As  to  the  result,  Admiral  Bahlgren  reported:  "I^o 
ship  had  been  exposed  to  the  severest  fire  of  the 
enemy  over  forty  minutes,  and  yet  in  that  brief  period 
five  of  the  iron-clads  were  wholly  or  partially  dis- 
abled ;  disabled,  too,  in  that  which  was  most  essential 
to  our  success — I  mean  in  their  armament  or  power 
of  inflicting  injury  by  their  guns.  .  .  .  The  other 
iron-clads  (2  out  of  7),  though  struck  many  times 
severely,  were  still  able  to  use  their  guns,  but  I  am 
convinced  that  in  all  probability  in  another  thirty 
minutes  they,  too,  would  have  been  likewise  dis- 
abled." 

The  official  rej)orts  of  the  captains  commanding 
the  iron-clads  indicate  that  the  fleet,  exclusive  of  the 
Bew  Ironsides^  received  346  hits.  The  New  Ironsides 
was  struck  several  times,  but  the  exact  number  ap- 
pears not  to  have  been  reported.  The  KeoJculc  was 
sunk,  where  her  guns  were  subsequently  secured  by 
the  Confederates.  One  man  was  killed  and  at  least 
twenty-two  men  were  wounded  on  shipboard  during 
the  action. 

Upon  the  Confederate  side,  General  Beauregard 
states:  "Not  more  than  34  shots  took  effect  on  the 
walls  of  Fort  Sumter."  "Fort  Moultrie  and  other 
batteries  were  not  touched  in  a  way  to  be  considered." 
The  injuries  to  Fort  Sumter  were  by  no  means  dis- 
abling, and  the  total  casualties  on  land  were  three 
men  killed  by  the  accidental  explosion  of  an  ammu- 
nition-chest, and  eleven  men  wounded—  five  of  them 
by  the  same  accident. 

The  next  conspicuous  duel  between  armored  ships 
and  forts  was  at  Fort  Fisher,  North  Carolina.  This 
fort  had  a  water-front  and  a  land-front,  both  consist- 
ing of  substantial  sand  batteries ;  the  land-front  had 


Frobable  Nature  of  the  AttacJc.  31 

an  oblique  lire  upon  the  sea.  The  worli  was  well 
provided  with  traverses  and  bomb-proofs,  but  the 
former  were  so  conspicuous  that  they  marked  the  gun 
positions  with  great  distinctness.  The  site  was  a  low, 
sandy  point  between  the  ocean  and  Cape  Fear  River. 
The  offing  afforded  unlimited  development  to  the 
fleet. 

Carrying  out  the  plan  of  a  co-operative  attack  in 
aid  of  tlie  land  forces,  Admiral  Porter  ordered  his 
monitors  to  anchor  at  a  range  of  about  800  yards,  and 
his  wooden  vessels  in  three  lines  at  from  1  100  to 
1  800  yards.  Tlie  former  were  to  fire  deliberately 
upon  the  land-front  (from  within  a  dead  angle  where 
the  enemy  could  reply  only  at  great  disadvantage)  in 
order  to  prepare  the  way  for  an  assault ;  the  latter 
were  to  maintain  so  terrific  a  storm  of  shot  and  shell 
over  the  fort  as  to  prevent  the  enemy  from  serving 
his  guns.  These  tactics  were  successful,  and  the 
Confederates  were  soon  driven  to  take  temporary 
refuge  in  their  bomb-proofs. 

Immediately  after  the  capture  of  the  fort  on  Jan- 
uary 15,  1865,  I  personally  made  an  inventory  of  the 
armament,  with  notes  as  to  its  condition.  The  fol- 
lowing were  the  water-bearing  guns  :  On  the  land 
front,  one  10-inch  Rodman,  five  8-inch  Rodmans, 
five  old  32-pounders,  one  old  24-pounder,  seven  6.4- 
inch  rifles,  one  4.2-inch  rifle  ;  total,  20  guns.  On  the 
water-front,  nine  10-inch  Rodmans,  four  8-inch  Rod- 
mans, two  8-inch  rifles,  two  7-inch  rifles,  five  6.4-inch 
rifles  ;  total,  22  guns.  The  grand  total  which  could 
have  been  used  against  the  fleet  was  42  guns.  Of 
these,  eight  guns  and  eight  carriages  (16  in  all)  were 
disabled  on  the  land-front,  and  one  gun  on  the  water- 
front (it  evidently  had  burst  in  action).  This  state- 
ment includes  all  injuries  by  direct  impact  of  shot, 
or  by  destruction  of  carriages,  or  by  the  ■i:)iling  of 
sand  in  front  of  the  guns  ;  they  represent  the  wliole 


32  General  Considerations. 

damage  effected  by  one  of  tlie  most  tremendous  bom- 
bardments of  modern  times  directed  against  an  open 
barbette  battery  on  a  low  site. 

The  following  was  the  effective  armament  of  the 
fleet,  as  furnished  to  me  by  the  Bureau  of  Ordnance, 
Navy  Department.  It  includes  all  the  pivot  guns 
and  half  the  broadside  gans  of  the  vessels  in  ac- 
tion, excluding  the  small  bronze  guns  as  of  no  value 
for  such  service  :  ten  15-inch  Dahlgrens,  20  11-inch 
Dahlgrens,  two  10  inch  Dahlgrens,  one  hundred  and 
thirty-four  9-inch  Dahlgrens,  eighteen  8-inch  Dahl- 
grens, sixteen  32-pounders,  eight  8-inch  Parrott  rifles, 
twenty-four  100-pounder  Parrott  rifles,  two  60- 
pounder  Parrotts,  two  50-pounder  Dahlgrens,  twen- 
ty-seven 30-pounder  Parrotts,  twelve  20-pounder 
Parrotts,  making  a  total  of  275  guns  of  all  calibres 
used  against  the  land  defences. 

This  bombardment  silenced  the  Are  of  the  fort  and 
enabled  an  assault  to  be  delivered  without  the  pre- 
liminary operations  of  a  siege — an  assistance  of  the 
most  important  character  ;  but  that  the  damage  to 
the  works  should  be  as  unimportant  as  it  actually 
was,  seemed  at  the  time  almost  incredible  to  the  eye- 
witnesses. If  the  garrison  had  not  been  provided 
with  ample  bomb-proofs,  a  surrender  might  probably 
have  occurred  ;  but,  as  it  was,  the  men  took  shelter 
until  the  flre  slackened  to  favor  the  assault,  and  then 
they  exhibited  anything  but  demoralization.  Still, 
it  must  not  be  forgotten  that  such  a  result  to-day 
would  be  decisive  in  favor  of  an  attack  to  force  a 
passage  ;  for  unless  the  land  guns  can  be  served  con- 
tinuously the  flanking  arrangements  will  be  destroy- 
ed, and  the  mines  will  be  removed  with  but  little 
risk. 

These  three  examples,  concerning  which  all  the 
essential  facts  are  known,  have  been  selected  as  typi- 
cal contests  between  guns  ashore  and  guns  afloat  at 


Probable  Nature  of  the  Attack.  33 

the  beginning  of  tlie  era  of  armor  and  of  heavy  guns 
on  shipboard.  They  certainly  prove  that  our  iron- 
clad fleet  could  not  contend  with  any  chance  of  suc- 
cess against  an  equal,  or  even  against  a  very  inferior, 
land  armament. 

The  same  was  true  at  that  epoch  in  Europe,  as 
appears  from  the  result  of  the  attack  of  the  Italian 
fleet  upon  the  island  of  Lissa  in  July,  1866.  Al- 
though full  data  respecting  this  two-day  engagement 
are  lacking,  enough  is  known  to  justify  the  claim  of 
the  Austrians  "of  having  driven  back  the  Italian 
iron-clad  ships,  incapable  of  resisting  the  fire  of  the 
forts  which  command  the  harbor."  Just  as  a  third 
attack  was  about  to  be  made,  including  a  landing  of 
troops  to  storm  the  works,  the  arrival  of  the  Aus- 
trian fleet  terminated  the  attempt. 

The  land  works  consisted  of  masonry  forts  and 
earthen  batteries,  which  appear  to  have  usually  had 
high  sites.  They  were  distributed  among  three  har- 
bors, and  "the  whole  of  the  defence  presented  a 
front  of  nearly  100  guns."  The  latter  were  all  of  an 
old  type,  of  which  the  largest  were  smooth- bores 
throwing  solid  shot  weighing  ^^  pounds,  and  rifles 
throwing  elongated  shot  weighing  60  pounds. 

The  armored  fleet  consisted  of  12  ships,  carrying 
248  guns.  Their  armament  "contained  all  the  latest 
improvements  which  the  modern  art  of  war  had  up 
to  that  date  invented."  There  were  also  8  unarmor- 
ed  ships  carrying  360  guns,  and  16  despatch-boats. 

The  bombardment  of  Alexandria  affords  the  only 
example  available  for  testing  more  recent  progress, 
and  even  that  fails  to  exhibit  what  the  latest  type  of 
guns  can  accomplish  against  land  batteries. 

The  foits  at  Alexandria  were  mostly  low  barbette 
batteries,  with  a  few  old  masonry  works  still  less  de- 
fensible against  modern  attack.  The  garrison  was 
demoralized  by  being  in  rebellion  against  its  own 


34  General  Considerations. 

government,  which  was  supported  by  the  hostile  fleet. 
The  only  circumstance  in  favor  of  the  rebels  was  the 
possession  of  a  few  Armstrong  guns. 

On  the  northern  line  there  were  20  Armstrong 
M.  L.  rifles  (four  10-inch,  nine  9-inch,  five  8-inch,  and 
two  7-inch),  thirteen  40-pounder  Armstrong  B.  L. 
rifles,  and  62  smooth-bores  which  were  little  used. 
On  the  inner  line  there  were  seven  Armstrong  M.  L. 
rifles  (one  10-inch,  one  9-inch,  and  five  8-inch),  with 
one  40-pounder  Armstrong  B.  L.  rifle,  and  76  smooth- 
bores which  were  little  used. 

The  working  broadside  of  the  offshore  squadron 
opposed  to  the  northern  line  the  fire  of  '^^  M.  L.  rifles 
(two  16-inch  81-tons,  one  12-inch  25-tons,  fifteen  10- 
inch  18  tons,  two  9-inch  12-tons,  and  six  8-inch  9- 
tons).  These  were  supplemented  later  by  three  more 
of  25  tons,  two  of  18  tons,  and  two  of  81  tons. 

The  working  broadside  of  the  inshore  squadron 
employed  th6  following  heavy  guns,  all  muzzle-load- 
ing rifles :  four  12-inch  of  25  tons,  five  9-inch  of  12 
tons,  and  four  8-inch  of  9  tons  ;  total,  13  guns. 

In  Captain  Goodrich's  Keport,  from  which  these 
data  are  extracted,  is  a  table  of  numerical  ratios 
showing  'Hhe  phases  which  the  engagement  either 
assumed  or  might  have  been  made  to  assume."     It  is  : 

Fort  Pharos 4  land  to  33  ship  (actual). 

Fort  Adda 5  land  to  28  or  33  ship  (actual). 

Bas-el-Tin  Lines. .  7  land  to  26  ship. 
Light-house  Fort .  4  land  to  26  ship. 
Fort  Mex 5  land  to  14  or  16  ship  (actual). 

Taking  into  consideration  the  relative  calibres  as 
well  as  numbers,  it  is  plain  that  this  action  affords 
no  fair  comparison  between  the  fire  of  guns  on  land 
and  those  on  shipboard  ;  but  it  has  value  as  a  test  of 
the  effect  of  modern  guns  on  batteries  of  the  kind 
engaged.    Three  thousand  one  hundred  and  ninety- 


Probable  Nature  of  the  Attack.  36 

eight  rounds,  of  which  1  731  were  7  inches  and  up- 
ward in  calibre,  were  fired  by  the  fleet.  Captain 
Goodrich  writes:  "To  the  unprejudiced  observer 
the  most  striking  characteristics  of  the  bombardment 
^re,  without  doubt,  the  excessive  apparent  and  the 
slight  real  damage  done  to  the  fortifications.  .  .  ." 
"The  forts  at  Alexandria  were  badly  bruised,  but 
the  more  modern  parapets  were  not  seriously  harmed. 
In  the  generality  of  cases  the  real  damage  they  sus- 
tained could  have  been  easily  repaired  in  a  single 
night.  If  the  bombardment  was  directed  against  the 
forts  in  this  their  defensive  capacity,  it  must  be  pro- 
nounced a  failure.  If  its  object  was  the  dismounting 
of  the  new  rifled  guns,  it  must  be  conceded  that  such 
results  as  attended  the  work  of  the  inshore  squadron 
(only  one  gun  of  this  type  being  seriously  affected), 
or  even  such  as  were  achieved  by  the  offshore  squad- 
ron (less  than  one-half  being  permanently  disabled), 
do  not  justify  the  verdict  of  success." 

The  action  at  Alexandria,  rightly  or  wrongly,  has 
certainly  tended  to  reduce  the  estimate  lately  enter- 
tained by  engineers  as  to  the  accuracy  of  fire  to  be 
expected  from  shrapnel  and  machine  guns  on  modern 
ships  of  war — the  peace  practice  at  Inchkeith  notwith- 
standing. Although  siege  howitzers  on  land  have 
proved  their  ability  to  breach  concealed  scarps  and 
rsearch  out  nopks  and  corners  of  fortresses  with  show- 
ers of  descending  shrapnel-balls,  it  now  appears  that 
no  such  practice  is  to  be  apprehended  from  vessels. 
Although  machine  and  rapid-firing  guns  are  murder- 
ous at  suitable  ranges  on  land,  their  fire  proved  to  be 
far  less  terrible  from  the  gunboats.  Moreover,  this 
fire  can  be  neutralized  by  forbidding  an  approach  to 
within  less  than  1  000  yards.  In  addition,  it  has  been 
practically  learned  that  high-power  guns,  with  their 
flat  trajectories,  are  unfavorable  for  shrapnel-fire 
;against  earth-works.    The  spread  of  the  balls  is  be- 


36  General  Considerations. 

lieved  to  be  often  less  tlian  live  degrees,  and  mucli  of 
the  effect  depends  on  obtaining  a  rapid  fall  in  the 
shell  itself  before  explosion.  General  Sir  Andrew- 
Clarke,  R.  E.,  late  Inspector-General  of  Fortifications, 
sums  up  a  recent  discussion  of  the  subject  with  this 
language:  ''As  regards  searching  effect,  ships  are 
now  in  a  worse  position  than  they  w^ere  fifty  years 
ago,  and  when  re-armed  with  new  guns  tlieir  power 
will  in  this  respect  be  still  further  diminished."  He 
also  states:  ''At  Alexandria  the  fieet  carried  about 
seventy  1-inch  4-barrel  I^ordenfelts  and  expended 
more  than  16  000  bullets.  The  expenditure  of  Gat- 
ling  ammunition  was  only  7  000  rounds,  and  of  Mar- 
tini bullets  10  000.  As  to  the  results  obtained  opin- 
ions differed.  It  is  submitted,  how^ever,  that  the 
number  of  hits  on  the  guns  and  carriages  of  the  de- 
fence may  fairly  be  taken  to  afford  some  indication 
of  those  results.  The  hit  of  a  Nordenfelt  bullet  on 
iron  is  generally  unmistakable,  but  it  is  evidently 
possible  that  grazes  at  a  very  acute  angle  might  have 
escaped  observation.  The  total  number  of  hits  on 
guns  and  carriages  was  seven,  and  even  this  mode- 
rate number  requires  qualification." 

I  think,  after  this  review  of  the  best  data  upon  the 
subject,  no  one  will  advocate  a  fixed  ratio  of  compa- 
rison between  the  efficiency  of  guns  ashore  and  guns 
afioat.  The  Engineer  must  carefully  consider  the 
question  for  his  local  problem  and  make  his  own  esti- 
mate, taking  into  account  the  natural  advantages  and 
disadvantages  of  the  position,  and  how  far  his  art  can 
be  applied  to  increase  the  relative  power  of  the  land 
armament.  One  consideration  must  not  be  overlooked 
for  a  position  of  first-class  importance,  especially 
when  the  approaches  are  unfavorable  to  the  fleet. 
The  enemy  may  not  be  able  to  bring  all  his  force  to 
bear  at  the  same  time,  but  his  reserves  may  be  able  to 
supply  losses  and  maintain  the  attack  with  unbroken 


IB     vigor ; 


Probable  Nature  of  the  Attack,  37  ^ 


vigor  ;  while  the  land  batteries,  having  no  reserves,  will 
become  less  and  less  able  to  meet  it  as  their  guns  be- 
come dismounted. 

Personally,  while  according  a  relatively  higher 
efficiency  to  naval  armaments  as  compared  with  land 
guns  than  was  warranted  by  experience  before  recent 
improvements,  I  am  convinced  that  ship  guns  can 
never  hope  to  contend  with  similar  land  guns  on  any- 
thing like  equal  terms  when  the  latter  are  properly 
placed  in  position  and  properly  served.  In  fine,  I 
think  engineers  would  agree  tliat  for  a  port  of  first- 
class  importance  the  armament  should  never  be  al- 
lowed to  fall  below  that  of  the  enemy  in  calibre,  and 
that  in  number  of  guns  we  should  rarely  mount  less 
than  half  of  what  can  be  deployed  against  the  works 
in  line  of  battle.  With  such  an  armament,  well  dis- 
posed upon  a  favorable  site,  and  well  served,  I  should 
have  no  fear  of  the  result,  and  indeed  one  much 
weaker  would  have  a  fair  chance  for  success. 

It  only  remains  to  consider  how  a  land  position  is 
likely  to  be  attacked  by  a  fleet. 

Naval  Tactics  against  Forts. — At  Port  Royal, 
in  November,  1862,  Admiral  Dupont  captured  the 
land  defences  (Forts  Walker  and  Beauregard)  by  a 
system  of  tactics  which  consisted  in  keeping  his  fleet 
(unarmored)  in  constant  motion  upon  an  elliptical 
curve  which  brought  the  ships  within  a  range  of 
about  half  a  mile  of  the  forts  in  passing.  These 
forts,  armed  with  35  small  guns,  only  two  being  rifled, 
were  earthen  batteries  of  slight  command  and  ill- 
fitted  to  endure  so  powerful  an  attack  as  that  of  his 
squadron.  Still,  at  that  date  these  tactics  were 
highly  admired,  and  were  even  claimed  by  some  en- 
thusiasts to  mark  a  new  era  in  such  operations. 

Similar  tactics  were  tried  at  Alexandria  in  1882^ 
the  speed  being  about  five  miles  per  hour,  but  with- 
out a  satisfactory  result.     Captain  Goodrich  states  : 


38  General  Considerations. 

V  The  outside  squadron  having  tried  both  modes  of 
attack,  under  weigh  and  at  anchor,  definitely  solved 
one  important  problem.  There  remains  no  possible 
doubt  that  ships  engaging  forts  not  superior  to  them 
in  force  will  gain  more  in  accuracy  of  fire  by  anchor- 
ing than  in  safety  by  keeping  under  way."  These 
views  accord  with  statements  of  Royal  Engineer  offi- 
cers and  with  my  own  belief  ;  for  I  think  that  land 
guns  will  hereafter  be  so  protected  in  positions  of 
importance  that  they  will  have  little  to  fear  from  the 
inaccurate  practice  inseparable  from  motion. 

Accepting,  then,  as  a  maxim  that  a  first-class 
naval  attack  upon  a  well-fortified  position  will  be 
made  at  anchor,  or  at  any  rate  from  fixed  buoys  to 
indicate  the  precise  range  to  the  gunners,  the  defence, 
aided  by  the  modern  system  of  position-finding,  can 
count  upon  all  the  advantages  resulting  from  supe- 
rior stability  of  platform,  freedom  from  the  annoy- 
ance of  smoke,  and  a  better  knowledge  of  the  range. 

But  what  ranges  will  ships  select  when  the  chan- 
nel allows  a  choice  %  The  preponderance  of  profes- 
sional opinion  is  that  it  will  be  as  short  as  the  power 
of  the  land  guns  will  permit.  If  that  power  be  in- 
sufficient to  penetrate  the  armor,  ships  will  approach 
very  closely  to  increase  their  precision  of  fire  as 
much  as  possible.  Their  targets  are  guns  and  maga- 
zines, and  all  shots  that  fail  to  attain  them  are 
thrown  away,  although  great  apparent  damage  may 
result  to  earthen  parapets  and  to  masonry  walls. , 

At  Lissa  the  fleet  forced  the  fighting,  ranges  of 
300  and  400  metres  being  mentioned  in  the  report. 

At  Alexandria  the  outside  squadron  began  the 
action  at  a  minimum  range  of  about  1  500  yards.  Of 
the  inshore  squadron  the  flagship  was  anchored  at 
1  300  yards,  while  the  Penelope  drifted  several  times 
broadside  on  from  that  distance  to  700  yards.  The 
Inflexible  and  Temeraire  fired  at  very  much  greater 


Probable  Nature  of  the  Attack,  39 

distances — between  3  000  and  4  000  yards.  These 
long  ranges  were  criticised  by  Captain  Goodricb  as 
"needlessly  great."  He  states:  ''The  outside  ves- 
sels could  have  gone  to  within  1  000  yards  on  the 
northwest  side  of  the  Light-house  fort  and  800  yards 
abreast  the  Ras-el-Tin  lines  ;  to  within  500  yards  of 
Fort  Adda  and  200  yards  of  Fort  Pharos.  Along 
the  southern  line  the  ships  could  easily  have  gotten 
within  400  yards  of  all  the  batteries.  This  would 
have  prevented  the  Temeraire  from  shelling  Mex, 
but  it  is  believed  that  the  gain  would  have  outbal- 
anced the  loss.  It  can  hardly  be  doubted  that  the 
boldness  of  this  move  would  have  been  rewarded  by 
the  speedier  and  more  extensive  dismounting  of  the 
guns,  which  was  confessedly  the  chief  object  of  the 
attack.  Shrapnel  and  canister  from  a  portion  of  the 
ships'  batteries,  supplemented  by  the  machine  guns 
at  a  more  appropriate  range  than  that  originally 
adopted,  would  have  prevented  return  fire  from  the 
shore ;  and  the  remainder  could  have  been  concen- 
trated on  each  gun  in  the  forts  in  succession  until 
bowled  over.  Close  range  and  a  stable  platform, 
however,  are  necessary  for  such  refinement  of  prac- 
tice." 

I  think  there  can  be  little  doubt  that  such  consid- 
erations will  commend  themselves  to  Naval  Com- 
manders ;  and  they  must  be  met  by  at  least  a  few 
guns  of  the  largest  calibre,  and  by  outlying  sub- 
marine mines  where  nature  permits  too  close  an 
approach  to  the  works.  A  shoal  in  the  near  front  is 
a  great  merit  in  a  position  for  a  battery.  The  ship 
must  necessarily  fight  under  disadvantages  as  to  pre- 
cision of  fire,  and  it  is  the  business  of  the  Engineer  to 
secure  the  full  benefit  of  this  advantage  by  forcing 
an  action  at  long  range. 

If  this  be  desirable  for  horizontal  fire,  it  is  abso- 
lutely essential  for  vertical  fire.     With  mortars  the 


40  General  Considerations. 

force  of  impact  depends  upon  the  fall  of  the  projec- 
tile, which  fall  is  a  direct  function  of  the  range ; 
hence  with  this  class  of  ordnance  very  short  ranges 
are  to  be  forbidden  to  the  enemy  at  any  cost. 

To  sum  up  these  conclusions  as  to  the  probable 
nature  of  an  attack  by  a  modern  fleet  upon  a  sea-coast 
fortress  of  the  first  class,  I  am  disposed  to  believe  : 
(1)  that  we  should  be  prepared  to  meet  the  largest 
calibres  which  the  draught  of  water  in  the  channel  will 
admit ;  (2)  that  from  five  to  ten  ships,  carrying  from 
thirty  to  sixty  guns  of  six- inch  calibre  and  upward, 
should  be  estimated  for  each  mile  of  the  line  of  battle 
— the  character  of  the  approaches  determining  the 
precise  number  ;  (3)  that  the  attack  will  be  made  at 
anchor,  or  at  least  from  fixed  buoys,  in  order  to  in- 
crease the  precision  of  fire ;  and  (4)  that  it  will  be 
made  at  as  close  quarters  as  possible.  The  Engineers 
should  provide  for  a  land  armament  at  least  equal  in 
calibre,  and  perhaps  half  as  large  in  number  of  guns, 
as  that  which  can  be  deployed  against  the  works.  All 
approach  to  within  less  than  1  000  yards  must  be 
forbidden,  use  being  made  of  submarine  mines  if 
deep  water  renders  them  necessary  for  this  purpose. 
Witli  a  reasonably  favorable  site,  well  occupied,  I 
consider  that  such  preparations  would  probably  de- 
ter attack  and  would  certainly  give  large  odds  in 
favor  of  the  land  defences. 


Lecture  IL 


ECOIVOMY  IN  COAST  DEFENCE. 

Limit  of  judicious  outlay — Economic  value  of  different  elements  ;  gen- 
eral analysis  ;  case  of  non-disappearing  barbette  mounting;  case  of 
the  King  mounting  for  50-ton  12-inch  rifle  ;  case  of  the  Duane  lift; 
case  of  an  armored  casemate ;  case  of  a  revolving  turret ;  general 
'    conclusions. 

Before  proceeding  to  consider  details  it  will  be 
well  to  discuss  with  some  care  the  fundamental  basis 
upon  which  they  all  rest.  Are  outlays  for  coast  de- 
fence demanded  by  the  needs  of  the  country  ;  and,  if 
so,  how  large  an  amount  should  be  asked  of  Con- 
gress ?  How  far  are  projects  for  coast  defence  to  be 
influenced  by  the  question  of  expenditure  ? 

LIMIT   OF  JUDICIOUS    OUTLAY. 

From  one  point  of  view  expenditures  for  sea- 
coast  defences  should  be  regarded  simply  as  a  neces- 
sary business  outlay  entailed  by  the  possession  of 
wealth,  and  should  be  governed  by  the  usual  rules  of 
Insurance,  so  far  as  they  can  be  applied.  A  citizen 
of  New  York  pays  a  certain  percentage  of  his  prop- 
erty towards  the  support  of  a  fire  department,  be- 
cause he  is  convinced  that  the  outlay  is  demanded  by 
true  economy  as  a  protection  against  loss  by  fire  ;  he 
pa\  s  another  tax  to  maintain  a  police  department  to 
afford  security  against  individual  violence  and  rob- 
bery ;  he  contributes  his  assessments  in  support  of 
the  National  Gruard,  because  he  knows  that  mobs  are 
a  danger  to  life  and  property  which  timely  precau- 
tions alone  can,  control ;   finally,   not  satisfied  with 


42  Economy  in  Coast  Defence. 

these  precautions,  his  business  instincts  teach  him  to 
pay  large  sums  for  insurance,  to  reimburse  him  for 
losses  which  may  probably  overtake  him  in  spite  of 
all  his  forethought.  It  seems  amazing,  to  one  who 
has  reflected  upon  the  subject,  that  this  same  man 
appears  to  forget  that  war,  liable  at  any  time  to 
occur,  may  result  either  in  the  burning  of  his  prop- 
erty under  circumstances  which  will  cripple  the  lire 
department,  disperse  the  police  and  National  Guard, 
and  bankrupt  the  insurance  companies,  or  else  will 
subject  him  to  enormous  impositions  to  purchase  ex- 
emption from  utter  destruction.  Surely  all  history 
proves  that  this  danger  is  real,  and  should  arouse 
public  sentiment  to  demand  that  the  lethargy  which 
for  a  dozen  years  has  paralyzed  us  shall  cease,  and 
that  the  general  government,  without  further  delay, 
shall  attend  to  its  duty  of  providing  for  the  national 
defence. 

It  must  not  be  overlooked  that,  in  some  important 
particulars,  funds  invested  in  sea  coast  fortresses  are 
far  more  advantageous  than  ordinary  insurance. 
Thus,  instead  of  merely  distributing  the  loss  among 
many  individuals,  they  prevent  it  altogether.  More- 
over, large  continuous  outlays  are  not  required.  The 
works  are  imperishable  and  the  annual  premiums  are 
therefore  small.  A  port  once  provided  with  ade- 
quate defences  remains  in  security  until  new  progress 
in  the  art  of  war  demands  modifications.  In  a  word, 
their  utility  is  as  permanent  as  anything  hum^n. 

But,  it  may  be  asked,  what  has  this  problem  in 
political  economy  to  do  with  the  duty  of  the  military 
engineer  \  I  answer.  Much.  He  should  regulate  his 
plans  and  estimates  upon  the  same  principles  which 
determine  the  size  of  the  fire  department,  the  strength 
of  the  police  force,  and  the  organization  of  the  Na- 
tional Guard.  His  problem  is  more  complex,  be- 
cause the  elements  are  more  uncertain,  the  field  is 


r 


Limit  of  Judicious  Outlay.  43 


broader,  and  constructive  damages  constitute  a  larger 
element ;  but,  after  all  is  said,  the  matter  reduces  it- 
self to  dollars  and  cents.  If,  ignoring  the  question 
of  cost,  the  engineer  demands  a  larger  outlay  than 
business  principles  will  warrant,  he  rightly  fails  to 
command  the  confidence  of  those  whose  duty  it  is  to 
scrutinize  the  necessity  for  expenditures  before  vot- 
ing appropriations. 

When  preparing  a  project  for  defence  the  first 
matter  for  consideration  is,  therefore,  what  sum  can 
judiciously  be  expended.  This  by  no  means  signifies 
exact  figures,  like  those  for  the  cost  of  a  mass  of  con- 
crete or  of  an  iron  shield ;  there  are  many  elements 
to  be  considered,  some  of  which  can  be  measured  by 
the  gold  standard,  while  others  can  hardly  be  so 
gauged.  As  an  example  of  the  first  class,  the  port 
may  contain  a  great  city,  and  the  assessed  valuations 
for  real  estate  and  personal  property  are  always  ac- 
cessible, while  fair  estimates  of  the  value  of  exempt 
and  untaxed  real  estate  and  personal  property  may 
usually  be  obtained  with  some  degree  of  exactitude. 
If  a  hostile  fleet  succeeds  in  forcing  its  way  into  the 
harbor,  the  property  which  lies  at  its  mercy  will 
either  be  destroj^ed  or  will  be  ransomed  at  a  price 
which  may  range,  according  to  circumstances,  even 
up  to  a  full  cash  valuation  of  all  property  subject  to 
destruction.  This  valuation,  of  course,  will  exclude 
the  cost  of  land,  of  water- works,  of  gas-mains,  of  roll- 
ing stock  of  railways,  of  bonds  and  specie,  and  of 
all  other  non-destructible  or  removable  property. 
What  is  needed,  therefore,  by  the  engineer  in  his 
estimates  for  this  class  of  probable  damages  is  a  fair 
valuation  of  the  total  destructible  property. 

When  preparing  a  paper  on  Coast  Defence  which 
was  read  before  the  Military  Service  Institution  in 
1885,  Captain  Eugene  Griffin,  Corps  of  Engineers, 
corresponded  with   collectors  and  receivers  of  taxes, 


,44  Economy  in  Coast  Defence, 

boards  of  assessment,  and  collectors  of  ports,  and 
consulted  reports  of  Tax  Departments  and  other 
official  documents  of  a  similar  character,  with  a  view 
ito  obtain  a  fair  estimate  of  the  destructible  property 
-exposed  to  an  enemy  in  eight  of  the  eleven  ports  af- 
terward (1886)  reported  by  the  Endicott  Board  as 
''  most  urgently  requiring  fortifications  or  other 
defences."  The  three  ports  not  included  were  the 
Xiake  ports,  Hampton  Roads,  and  Washington. 

Captain  Griffin  presents  the  results  of  his  re- 
^searches  in  tabular  form  ;  and  they  convey  much 
information  useful  for  reference  in  this  connection. 
The  figures  are  based  on  valuations  for  the  year  1884, 
ithree  years  ago.  But  the  records  show  that  during 
the  past  ten  years  there  has  been  in  New  York  City 
an  average  annual  increase  of  $40  000  000  in  the  total 
assessment  valuation  for  real  estate  and  personal 
property.  Last  year  this  increase  was  $50  000  000. 
We  should  therefore  accept  Captain  Griffin's  figures 
as  now  considerably  under  the  true  values. 

His  grand  total  of  destructible  property  for  these 
-eight  ports  (Portland,  Boston,  Newport,  New  York, 
Philadelphia,  Baltimore,  New  Orleans,  and  San  Fran- 
cisco) is  $4  529  177  244.  The  estimate  of  the  cost  of 
fortifying  these  same  eight  ports  upon  a  liberal  scale, 
presented  by  the  Endicott  Board  (including  $18  875- 
000  for  five  floating  batteries  and  their  armament,  to 
be  used  at  San  Francisco  and  New  Orleans),  is 
$90  018  150,  or  a  gross  sum  not  quite  two  per  cent,  of 
the  value  of  the  destructible  property  now  at  the 
mercy  of  any  maritime  enemy.  Extending  these 
expenditures  over  a  term  of  ten  years,  as  is  projjosed, 
they  would  amount  to  an  annual  expenditure  of 
two-tenths  of  one  per  cent,  of  the  destructible  prop- 
erty. 

Let  us  now  see  how  this  compares  with  the  pre- 
miums paid  for  other  insurance  in  New  York.     The 


Limit  of  Judicious  Outlay,  45 


City  pays  over  $1  500  000  annually  for  the  support  of 
its  lire  department  and  over  $6  000  000  annually  for 
insurance  against  fire— aggregating,  say,  $7  500  OOO. 
It  pays  over  $500  000  annually  for  its  courts,  its  pri- 
sons, and  the  support  of  its  criminal  classes,  and  over 
$4  500  000  annually  for  its  police  department— or  a 
total  of  upward  of  $5  000  000  as  its  insurance  against 
minor  disorders  and  robbery.  The  cost  of  the  Na- 
tional Guard,  which  represents  insurance  against 
mob  violence,  is  not  less  than  $617  000,  of  which  the 
State  pays  $400  000  for  cost  of  camp-ground,  pay  of 
troops  in  camp,  annual  allowance  for  clothing,  drills, 
etc.;  the  county  contribution  for  rent  of  armories, 
janitors,  etc.,  in  New  York  and  Brooklyn,  is  $117  000  ; 
the  balance,  $100  000,  is  the  estimated  private  outlay 
of  the  members  themselves. 

The  aggregate  annual  insurance  against  these 
three  dangers,  fractions  included,  is,  say,  $13  800  000. 
The  corresponding  total  destructible  property  in  1884 
was  $1  855  303  043.  The  total  annual  insurance 
against  these  ordinary  dangers  in  the  City  of  New 
York  is,  therefore,  eight-tenths  of  one  per  cent,  of  its 
destructible  property,  or  four  times  the  percentage 
proposed  as  an  annual  expenditure  for  ten  years  for 
the  most  important  coast  defences  of  the  Nation. 

The  financial  question,  therefore,  resolves  itself 
into  this  :  Is  it  or  is  it  not  judicious  for  the  Nation  to 
pay  in  ten  years  for  protecting,  during  a  term  of 
many  years,  the  property  exposed  to  destruction  in 
its  eight  principal  ports,  as  high  a  premium  as  New 
York  pays  continuously  every  2.5  years  to  protect 
itself  against,  loss  by  tire,  by  robbery,  and  by  vio- 
lence \  It  would  certainly  appear  that  business  prin- 
ciples demand  such  an  expenditure. 

But  this  basis  for  considering  tlie  matter  is  a  very 
inadequate  one,  even  from  a  financial  point  of  view. 
The  Nation  is  bound   to   supply   its  coasting  trade 


46  Economy  in  Coast  Defence. 

with  some  refuge  from  cruisers  in  case  of  war  ;  and 
this  cannot  be  done  so  long  as  even  its  chief  ports  are 
open  to  the  enemy.  The  same  remark  is  true  now, 
and  must  remain  so  for  some  years,  even  for  the 
Navy  itself.  Our  navy-yards  are  all  exposed  to  sud- 
den raids.  We  are  even  debarred  from  seeking  re- 
prisals with  our  new  cruisers  ;  for,  with  our  port& 
open  to  the  enemy,  we  should  pay  in  cash  for  every 
capture  as  soon  as  it  was  made.  Precedents  for  this 
ready  mode  of  keeping  our  Alahamas  in  check  are 
not  wanting ;  for  a  similar  system  was  enforced 
against  France  during  the  late  war,  to  protect  bodies 
of  German  cavalry  scouting  through  the  country. 

But  if  these  interests,  which  can  be  measured  in 
dollars  and  cents,  demand  attention  by  every  recog- 
nized business  i)rinciple,  how  shall  we  estimate  the 
National  humiliation  we  invite  by  slumbering  on  in 
our  present  unprotected  condition,  while  the  rest  of 
the  world  is  so  actively  awake  ?  The  stars  and 
stripes,  held  aloft  at  so  fearful  a  cost  twenty-five 
years  ago,  are  now  exposed  to  insult  by  second  and. 
third-rate  powers  whose  geographical  positions,  even, 
are  hardly  known  to  our  populace.  If  this  exposure, 
so  well  understood  by  Army  and  Navy  men,  were 
appreciated  by  the  country  at  large,  should  we  have 
been  allowed  to  sink  to  such  a  condition  % 

I  dwell  upon  this  branch  of  my  subject  because 
the  facts  should  be  emphasized,  (1)  that  there  is  ur- 
gent necessity  for  action  ;  and  (2)  that  engineers 
limit  their  estimates  for  coast  defence  to  reasonable 
sums.  The  nation  has  increased  so  rapidly  that  our 
people  still  gauge  their  ideas  of  military  exj)endi- 
tures  by  a  scale  long  since  outgrown.  Because  the 
sums  appear  large  when  stated  in  dollars  and  cents, 
the  enormous  interests  involved  are  forgotten  and  an 
outcry  of  extravagance  is  raised.  All  that  engineers 
demand  is  a  fair  hearing,  and  a  discussion  of  a  busi- 


Limit  of  Judicious  Outlay,  47 

ness  question  upon  business  principles  and  in  a  busi- 
ness-like way. 

Before  quitting  tlie  subject  let  us,  to  fix  ideas, 
attempt  to  consider  a  little  more  mathematically  the 
problem  what  stlm  {x)  the  nation  ought  to  expend 
annually  on  its  fortifications — every  consideration 
which  cannot  be  measured  by  a  gold  standard  being 
ignored. 

Clearly  this  sum  will  be  directly  proportional  to 
the  value  ( F)  of  the  property  exposed  to  capture, 
and  directly  proportional  to  the  average  frequency 
of  war  with  maritime   powers,    which    may  be  ex- 

W 

pressed  by  the  fraction  p-  ,  in  which  W  denotes  the 

number  of  years  of  war,  and  F  the  number  of  years 
of  peace,  noted  during  a  period  sufficiently  long  to 
afford  a  fair  average.  The  sum  to  be  expended  will 
be  inversely  proportional  to  the  efficiency  of  the  ex- 
isting defences,  which   may  be  represented  by  the 

fraction  -; — -,  in  which  B  denotes  the  price  of  an 

adequate  system,  and  B,  the  part  of  this  price  already 
paid.  The  sum  to  be  properly  expended  will  also  be 
inversely  proportional  to  {F\  a  quantity  representing 
the  fear  of  our  retaliation  or  of  an  attack  by  other 
enemies  while  involved  with  us,  and  the  improbability 
of  our  own  inauguration  of  war.  Hence,  represent- 
ing by  (7  a  numerical  constant,  we  may  write  : 


X=: 


c  y^ 

S       .—        FFS 
F 


S—S, 


From  this  equation  it  appears  that  x  can  be  zero  ; 
i.e.,  that  the  Nation  can  afford  to  pay  nothing  for 
defences,  only  upon  the  condition  that  W  =:  0,  or 
that  Sz=:  S^,  or  that   Z^=  co  ;    or,   in   other  words. 


48  Economy  in  Coast  Defence. 

wlien  the  millennium  has  come,  or  when  adequate 
defences  are  completed,  or  when  every  maritime 
power  so  dreads  our  strength,  or  the  hostility  of  its 
neighbors,  that  our  wealth  offers  no  sufficient  tempta- 
tion to  declare  war  against  us  or  to  give  just  provo- 
cation for  war  on  our  part.  But  few  will  claim  that 
wars  have  ceased,  or  that  our  defences  are  perfect,  or 
that  our  naval  power  is  so  vast  as  to  spread  terror 
throughout  the  world.  The  uncertainty  of  the  rela- 
tions between  the  great  powers  was  probably  our 
salvation  during  the  civil  war;  but  it  is  a  slender  reed 
upon  which  to  rest  our  only  hope  when  our  exposed 
wealth  is  measured  in  thousands  of  millions,  and  is 
increasing  with  wonderful  rapidity  from  day  to  day. 
Moreover,  it  will  be  noted  that  this  condition  {F  = 
00 )  implies  that  we  have  made  up  our  minds  to  en- 
dure any  insult  or  outrage  rather  than  have  recourse 
ourselves  to  the  ultima  ratio  regum.  The  Monroe 
doctrine  must  be  abandoned  ;  we  must  see  the  Sand- 
wich Islands  pass  under  a  foreign  protectorate,  if 
such  be  the  pleasure  of  a  commercial  rival ;  our 
fisheries  must  be  left  without  that  protection  which 
every  government  owes  to  its  citizens  ;  the  Isthmus 
canal,  when  completed,  may  be  used  to  discriminate 
against  us,  even  to  the  extent  of  ruining  our  commer- 
cial interests,  without  arousing  us  to  action ;  in  a 
word,  we  must  humble  ourselves  to  admit  that  we 
have  no  rights  which  any  nation  possessed  of  an 
armored  fleet  is  bound  to  respect.  That  the  Ameri- 
can people  will  ever  consent  to  occupy  a  position  so 
humiliating  is  a  supposition  not  to  be  named.  In- 
deed, the  belligerent  shrieks  which  are  always  raised 
by  newspapers  and  demagogues  when  our  foreign 
political  horizon  becomes  overcast,  and  the  excite- 
ment which  stirs  the  better  class  of  our  population  as 
well,  afford  ample  evidence  that  even  although  de- 
feat were  certain,  the  government  would  never  be  al- 


Limit  of  Judicious  Outlay.  49 

lowed  to  avoid  a  just  quarrel.  For  these  various 
reasons  we  cannot  assume  i^  =  go  ;  and  therefore, 
logically,  our  sea-coast  must  be  adequately  defended. 

But  let  us  go  a  little  further,  and,  by  assigning 
fair  numerical  values  to  the  quantities  in  this  general 
formula,  try  to  estimate  in  a  very  general  manner 
what  sum  business  principles  demand  shall  be  ex- 
pended next  year  upon  the  defences  of  New  York 
City.  Since  8,  is  practically  zero,  both  that  quantity 
and  /S' disappear.  From  Captain  Gfriffin's  researches, 
and  the  rapidly  increasing  wealth  in  the  City  during 
the  past  three  years,  Y  may  now  be  assumed  at 
$2  000  000  000.  One  consideration,  however,  must 
not  be  forgotten.  Although  this  amount  represents 
the  total  property  which  would  be  the  prize  of  a 
hostile  fleet  forcing  its  way  into  New  York  Harbor, 
and  which  at  its  option  might  be  destroyed,  a  much 
smaller  ransom  might  probably  be  accepted  ;  because 
a  certain  percentage  of  this  value  actually  carried  off 
in  gold  might  be  more  imi^ortant  to  the  captor  than 
the  forcing  of  a  larger  loss  upon  us.  What  per- 
centage might  be  demanded  as  a  ransom  would  de- 
pend upon  the  local  circumstances  of  the  case ;  bat 
certainly,  in  view  of  recent  similar  assessments,  ten 
per  cent.  ($200  000  000)  must  be  regarded  as  a  mode- 
rate demand. 

The  values  of  W  and  P  must  be  derived  from  our 
actual  experience  as  a  nation.  During  the  111  years 
which  have  elapsed  since  the  Declaration  of  Indepen- 
dence we  have  passed  about  nine  years  in  actual 
warfare  with  Great  Britain  ;  and  have  been  in  such 
imminent  danger  of  foreign  interference  during  the 
late  civil  war,  to  say  nothing  of  threatened  hostilities 
with  France  in  the  latter  part  of  the  last  century, 
and  with  Spain  on  several  recent  occasions,  that,  in 
prudence,  say  3  years  more  should  be  added.  Hence 
W  becomes  12,  and  F  becomes  99.     But  it  may  be 


50  Economy  in  Coast  Defence. 

objected  to  these  figures  that  our  present  strength  as 
a  nation  is  so  much  greater  than  it  was  in  the  earlier 
years  of  our  national  existence  that  they  afford  no 
fair  indication  for  the  future.  This  argument  might 
have  weight  if  our  offensive  power  upon  the  sea  had 
increased  ^ar/^a552^  with  our  wealth.  That  form  of 
national  strength  alone  can  be  considered,  since  our 
ability  to  raise  armies  on  land  does  not  enter  into 
the  problem  when  confronted  with  an  enemy  across 
the  water.  Offensive  power  upon  the  ocean  deters 
maritime  attack,  but  exposed  wealth  invites  it. 
Hence  it  is  the  ratio  between  these  quantities  at  dif- 
ferent periods  of  our  national  existence  which  is  to 
be  considered  :  and  it  may  safely  be  affirmed  that 
never  before  in  our  whole  history  has  this  ratio  been 
more  unfavorable  than  it  is  to-day. 

The  quantity  i^,  the  general  character  of  which  has 
already  been  considered,  is  more  difficult  to  express 
numerically.  Mathematically  it  is  a  ratio  of  which 
the  numerator  is  unity  and  the  denominator  a  pro- 
per fraction — i.e.,  the  denominator  is  zero  for  abso- 
lute security  and  unity  for  existing  war.  What  val- 
ue shall  be  assigned  is  a  matter  of  judgment ;  but 
perhaps  our  past  history  affords  the  fairest  measure. 
We  have  been  engaged  in  actual  war  (not  including 
Indian  wars)  about  one-seventh  of  our  national  exist- 
ence, and  I  shall  therefore  assume  F  to  be  — =7. 

Making  the  above  substitutions  in  the  formula,  an4 
noting  that  from  the  values  assumed  for  the  several 

quantities  C  becomes  — -,  we    have    the   numerical 

value : 

^  aiX_20W 000000X12^       4gg  j^g_ 
7X99 

But  this  sum  which,  upon  business  principles, 
should  be  expended  upon  the  defences  of  New  York 


Limit  of  Judicious  Outlay.  51 

€ity  during  the  coining  year,  exceeds  by  fifty  per 
<3ent.  the  amount  recommended  by  the  Endicott 
Eoard  [$2  394  850].  Hence  that  Board  under-esti- 
mated rather  than  over-estimated  the  business  risks 
and  necessities  involved  in  the  problem  of  the  de- 
fence of  New  York,  and,  more  generally,  in  that  of 
•our  sea- coast  and  Lake  frontier.  That  they  did  not 
ignore  financial  considerations  is  shown  by  the  fol- 
lowing quotation  from  their  report : 

''  A  comparison  can  now  be  made  of  the  estimates 
for  modern  works  with  those  made  in  1840,  when  the 
old  system  of  coast- defence  had  received  considerable 
-development  and  was  being  pressed  toward  comple- 
tion. The  population  of  the  country  at  that  time 
was  17  000  000,  and  the  estimate  of  cost,  including 
the  amounts  already  expended,  was  $57  131  541,  be- 
ing at  the  rate  of  $3.35  per  head. 

''The  population  in  1880  was  50  000  000,  and  the 
estimate  for  the  coast  defence  is  $126  377  800,  or  at 
the  rate  of  $2.52  per  head. 

''The valuation  of  property  in  1880  was  $43  642- 
'000  000  ;  that  of  1840  was  about  $4  000  000  000,  and 
it  is  to  be  seen  that  the  ratio  of  the  estimate  for  de- 
fences to  the  wealth  of  the  country  at  the  present 
time  exhibits  a  still  more  favorable  comparison. 

"In  1840  the  cost  of  the  line-of-battle  ship,  then 
representing  the  most  formidable  means  of  attack 
against  coast  defences,  was  about  $550  000,  and  the 
cost  of  the  corresponding  war-ship  of  the  present  day 
is  about  $5  000  000.  While  the  ships  have  increased 
in  cost  ninefold,  the  estimate  of  the  defences  to  re- 
sist them  has  increased  only  between  two  and  three 
fold." 

The  present  humiliating  condition  of  the  country, 
arising  from  the  neglect  of  this  subject,  can  hardly 
l)e  expressed  in  more  forcible  language  than  that  at- 
tributed to  Hon.  Robert  T.  Lincoln,  who  when  Secre- 


52  Economy  in  Coast  Defence. 

tary  of  War  was  in  a  position  to  have  his  attention 
officially  directed  to  the  matter.  He  is  quoted  as  re- 
cently saying:  '* During  my  term  as  Secretary  of 
War  you  recall  there  was  a  diplomatic  difficulty 
with  Chili.  I  was  in  trepidation  for  some  time  lest 
she  should  send  an  iron-clad  up  the  coast  and  exact  a 
heavy  tribute — millions  of  dollars,  in  fact — from  San 
Francisco,  under  threat  of  laying  the  city  in  ashes, 
which  she  could  easily  have  done.  Any  of  the  great 
naval  powers  of  the  world  could  do  such  a  thing — 
along  our  Atlantic  seaboard,  for  instance — in  case  of 
trouble.  Of  course,  had  we  entered  upon  war  with 
Chili,  she  would  have  got  the  worst  of  it  in  the  end  ; 
but  it  would  have  taken  time  enough  to  obtain  a  navy 
before  we  could  have  even  begun  offensive  opera- 
tions. In  point  of  fact,  there  is  much  latent  hostility 
against  us  among  foreign  nations,  and  it  would  often 
be  easy  to  bring  on  a  war.  But  we  are  not  in  condi- 
tion for  it,  and  all  the  world  knows  it.  Hence  our 
foreign  policy  lacks  self-respect  and  a  proper  asser- 
tion of  our  nation's  dignity  and  power.  We  would 
be  at  first  at  the  mercy  of  foreign  States  in  case  of 
hostilities,  and  our  government  has  to  be  humble  in 
its  diplomacy  in  consequence." 

ECOJS^OMIO  VALUE  OF  DIFFERENT  ELEMENTS. 

It  is  certain,  for  reasons  which  need  not  be  dis- 
cussed, that  in  this  country  appropriations  will  never 
exceed  a  fraction  of  the  sums  which  might  economi- 
cally be  applied  in  coast  defence.  Hence  not  only 
should  estimates  never  cover  extravagant  or  merely 
ornamental  work,  but  the  constant  aim  should  be  to 
provide  the  most  effective  and  economical  parts  of 
the  system  first.  In  a  word,  funds  must  be  applied 
where  they  will  yield  the  quickest  return  in  defensive 
strength.  By  following  this  course,  and  only  by  fol- 
lowing this  course,  will  the  engineer  be  acquitted  if 


Economic  Value  of  Different  Elements.       63 

disasters,  largely  resulting  from  ill-judged  parsimony 
in  appropriations,  should  hereafter  afflict  the  Nation. 

But  the  ground  is  sometimes  taken  that  where 
cost  comes  in  conflict  with  the  best  mode  of  fortify- 
ing a  particular  site,  cost  must  yield.  The  best  sys- 
tem must  be  adopted,  no  matter  at  what  expense.  If 
a  16-inch  gun  is  better  than  a  10-inch  gun,  it  must  be 
had  ;  if  a  turret  is  superior  to  a  lift  or  to  a  disappear- 
ing carriage,  it  must  be  built.  In  a  word,  cost  is  to  be 
considered  only  when  it  becomes  so  enormous  as  to 
forbid  any  hope  of  obtaining  the  needful  appropria- 
tions. In  my  judgment,  in  the  present  defenseless 
condition  of  the  coast  this  is  a  very  mistaken  view  of 
the  case. 

For  example,  suppose  a  million  dollars  were  grant- 
ed by  Congress  for  beginning  the  work  of  defending 
New  York  Harbor.  The  construction  of  a  turret  for 
two  110-ton  guns  on  the  site  of  Fort  Lafayette  would 
not,  in  my  judgment,  be  a  judicious  application  of  the 
money.  Such  a  turret  is  needed  and  should  be  built ; 
and  if  our  government  exhibited  as  much  interest  in 
Coast  Defence  as  does  Russia  or  Italy  it  would  cer- 
tainly be  promptly  built.  Still,  the  funds  could  be 
better  applied  under  the  peculiar  conditions  exist- 
ing here.  There  is  no  probability  of  our  being  able 
for  some  years  to  fabricate  110- ton  guns  ;  and  until 
we  can  do  so  the  turret  has  no  practical  value — for 
there  is  no  chance  that  Congress  will  import  guns 
from  Europe.  One  million  dollars  expended  in  sub- 
marine mines,  operating  casemates,  cable-shafts  and 
galleries,  mortar  batteries,  lifts,  and  disappearing- 
gun  batteries,  would  produce  a,  much  quicker  re- 
turn, and  would  at  least  enable  some  defence  to  be 
made,  and  at  a  much  earlier  date,  than  if  the  money 
were  sunk  in  the  turret. 

But  we  may  go  even  farther,  and  reach  the  same 
conclusion  upon  the  supposition  that  the  ordnance 


54  Economy  in  Coast  Defence, 

will  be  on  liand  ready  for  mounting  as  soon  as  the 
turret  is  completed.  No  doubt  a  turret  at  Fort  La- 
fayette mounting  two  110-ton  guns  would  have  enor- 
mous influence  in  deterring  an  attack  ;  but  thirty-two 
12-inch  rifled  mortars,  six  12-inch  rifles,  mounted 
say,  one  on  a  lift  and  five  on  disappearing  carriages, 
behind  substantial  earth  parapets,  and  an  effective 
system  of  mines,  with  casemates,  cable- galleries,  etc., 
complete,  all  of  which  could  be  provided  for  a  million 
dollars,  would  yield  a  better  return  for  the  invest- 
ment. 

I  dwell  upon  this  point  because  it  is  well  worthy 
of  consideration,  and  because  it  is  probable  that 
many  officers,  both  of  the  Army  and  Navy,  may  not 
entirely  agree  with  me.  We  see  clearly  what  is  the 
most  powerful  element,  and  are  inclined  to  insist  on 
procuring  it,  no  matter  what  may  be  the  cost.  If 
funds  were  liberally  provided  to  meet  the  needs  of  the 
service,  there  would  be  no  question  that  this  is  the 
right  principle  ;  but  we  know  to  our  sorrow  that  this 
is  not  the  habit  of  legislators.  Funds  are  given 
sparingly  and,  what  is  worse,  irregularly.  In  my 
judgment  they  should  be  applied  so  that  the  aggre- 
gate defensive  return  shall  be  the  greatest,  even  at 
the  temporary  sacrifice  of  some  of  the  more  expensive 
and  powerful  elements.  The  whole  case  may  be  put 
in  a  nutshell.  St)oner  or  later  war  will  surprise  us, 
and  we  shall  have  to  do  the  best  we  can  with  very  in- 
adequate means.  This  ought  not  to  be  so  ;  but  it  will 
be  so,  in  spite  of  all  efforts  to  the  contrary.  Hence, 
in  my  Judgment,  funds  should  now  be  applied  as  we 
shall  wish  that  they  had  been  applied  when  we  find 
ourselves  compelled  to  fight  with  but  few  chances  of 
success  in  our  favor.  An  Inflexible  would  be  a 
precious  possession  ;  but  I  think  the  50  first-class 
torpedo-boats,  which,  according  to  the  money  stan- 
dard, she  represents,  would  be  of  more  service  in  the 


Economic  Value  of  Different  Elements,       55 

defence  of  our  extensive  sea-coast  if  the  war-cloud 
were  to  burst  to-day,  or  at  any  time  within  half  a 
dozen  years,  and  very  probably,  indeed,  at  any  time 
within  the  next  twenty  years.  I  fear  we  shall  never 
have  the  coast  properly  defended  until  another  war 
like  that  of  1812  teaches  our  people  that  coast  de- 
fence is  a  live  issue.  In  a  paper  read  before  the 
Essayons  Club  of  the  Corps  of  Engineers,  many  years 
ago,  Major  W.  R.  King  discussed  this  question  ;  and 
I  quite  agree  with  his  conclusion  that  "cost  is  not 
only  a  proper  standard  of  comparison  in  engineering 
matters,  but  to  disregard  it,  or  to  speak  of  adopting  a 
certain  material  or  mode  of  construction  regardless  of 
cost,  is  simply  a  misapplication  of  terms."  Our  peo- 
ple thoroughly  understand  the  cash  standard  in  tlieir 
private  business,  and  we  must  do  the  same  in  this 
matter  of  coast  defence,  or  some  day  we  shall  rue  its 
neglect.  If  these  premises  are  sound  the  conclusion 
is  far-reaching  for  both  services. 

The  problem  of  a  new  Navy  is  under  solution  by 
naval  men.  The  Army  problem  is  now  before  us  for 
consideration  ;  and,  to  illustrate  the  principles  which, 
in  my  judgment,  should  govern  in  such  studies,  I  ask 
you  to  consider  how  a  gross  sum  to  be  expended  for 
the  defence  of  New  York  should  be  allotted  among 
different  objects  of  expenditure  ;  and,  to  simplify 
this  discussion,  I  will  limit  it  to  the  very  practical 
question.  How  should  one  million  dollars  be  expended 
in  purchasing  and  placing  in  position  12-inch  50-ton 
rifles  ? 

General  Analysis. — Evidently  the  maximum 
serviceable  number  of  guns  will  be  obtained  by 
placing  them  upon  simple  barbette  carriages  standing; 
upon  the  shore,  without  protection,  remote  from  each 
other,  and  with  no  provisions  for  loading  other  thau 
by  hand.  This  would  represent  one  extreme  solu- 
tion.    The  other  would  be  to  mount  one  gun  in  all 


56  Economy  in  Coast  Defence. 

the  security  and  with  all  the  facilities  for  rapid  load- 
ing.which  could  be  obtained  by  expending  the  whole 
balance  of  the  appropriation  on  these  accessories. 
Between  these  limits  what  would  be  the  most  econo- 
mical and  hence  the  most  judicious  investment  of  the 
iunds  ? 

I  shall  assume  three  fundamental  principles 
which,  although  perhaps  sometimes  modified  by 
special  conditions,  are  in  general  true.  They  are,  (1) 
that  the  object  to  be  sought  is  the  maximum  possible 
number  of  well-directed  shots  fired  against  the  en- 
emy during  the  engagement ;  (2)  that  the  economical 
value  of  a  gun-carriage  and  mounting  is  directly 
proportional  to  the  number  of  shots  it  permits  to  be 
;S0  fired,  provided  this  number  does  not  exceed  the 
limit  which  the  gun  can  safely  endure  ;  (3)  that  the 
economical  value  of  an  artificial  protection  for  the 
:gun  and  carriage  is  inversely  proportional  to  the 
•dangerous  area  through  which  it  permits  the  shot  of 
the  enemy  to  attain  essential  parts  of  the  mechan- 
ism. 

In  an  exhaustive  discussion  of  the  problem  other 
•elements  would  find  a  place — such,  for  example,  as 
diminished  efficiency  resulting  from  restricting  eleva- 
tion and  traverse  in  return  for  cover.  Practically, 
however,  these  are  believed  to  be  of  so  nmch  less 
importance  that  they  may  be  waived.  Thus  lifts  can 
be  arranged  for  an  all-round  fire  unlimited  as  to 
elevation  ;  a  revolving  turret  allows  a  full  traverse  of 
360  degrees,  and  all  the  elevation  (15  degrees)  which 
is  of  much  value  against  shipping ;  the  disappearing 
carriage  affords  only  about  120  degrees  in  traverse,  but 
is  unlimited  as  to  elevation  ;  in  fine,  the  armored  case- 
mate is  the  only  form  of  protection  now  advocated 
ivhich  seriously  restricts  the  field  of  fire.  But  few 
positions  demand  an  all-round  field  ;  and,  more  gen- 
erally, conditions  as  to  the  offensive  elements  of  the 


Economic  Value  of  Different  Elements,       57 

battery  are  so  dependent  on  the  particular  site  that 
they  may  be  ignored  in  a  general  discussion.  Lo- 
cally they  must  be  duly  considered  by  the  Engi- 
neer. 

In  reasoning  upon  such  questions  the  use  of  al- 
gebraic formulae  is  almost  a  necessity,  and  I  shall 
therefore  ask  your  indulgence  for  introducing  the 
method  here. 

Let 

c?=duration  of  engagement  in  minutes. 

^= minimum  interval  between  shots  which  the  gun 

will  endure. 
^,=interval  between  shots,  loading  by  hand. 
^//=interval  between  shots,  loading  by  stored  power. 
a=area  of  target,  in  square  feet,  presented  by  an: 

unprotected  gun  and  carriage. 
a^=area  of  target,  in  square  feet,  presented  by  a 

protected  gun  and  carriage. 
w=number  of  minutes  before  the  enemy  by  his  fire 
can  disable  the  unprotected  gun  and  carriage. 
m,=number  of  minutes  before  the  enemy  by  his  fire 

can  disable  the  protected  gun  and  carriage. 
F=cost  of  a  12-inch  50-ton  gun  mounted  without 

protection,  on  a  hand-loading  carriage. 
>S^=  funds  available    for    purchasing    and   placing 

in  position  12-inch  50-ton  rifies. 
a?= number  of  guns  that  should  be  mounted  with  J3,. 
^=: maximum  percentage  of  V  to  be  expended  in- 
increasing  rapidity  of  fire. 
J/=maximum  percentage  of   V  to  be  expended  for 
cover  of  gun  and  carriage. 
Considering  first  the  matter  of  rapidity  in  loadings 
we  have  for  the  number  of  rounds  fired   by  hand^ 

— ;  and  for  the  number  of  rounds  fired  by  stored 
^/ 

power,  — -.     The  difference  between  these  quantities 


58  Economy  in  Coast  Defence. 

will  be  the  number  of  rounds  gained  by  improve- 
ments in  loading,  providing,  of  course,  that  t^^  be  not 
made  less  than  t.  Factoring  this  gain,  one  factor 
being  the  number  of  rounds  with  hand-loading,  the 
other  {T)  will  express  the  maximum  fraction  of  Y 
which  can  economically  be  expended  for  machine- 
loading.    Hence  : 


d         d         d       t, —  t 


^11        ^/         ^/  ^// 

(1)     ^z=i=A/- 

IN'ext,  considering  the  question  of  cover  for  the 
gun,  by  following  the  same  course  of .  reasoning  as 
above  we  have : 


e->) 


M-- 


m,—m 
m 


But  since  m  :  m/.\a,  :  a^  the  numerical  value  of  this 
ratio  will  not  be  changed  by  writing  a^  for  m  and  a 
for  m,.     Hence : 

a  —  a, 


Jf= 


a. 


But  by  revolving  turrets,  by  lifts,  and  by  disap- 
pearing gun-carriages,  the  gun  and  carriage  may  be 
removed  entirely  from  the  sight  of  the  enemy  for  a 
greater  or  less  time  between  shots.  By  revolving 
turrets  and  lifts  its  protection  is  thus  nearly  absolute 
when  in  the  position  of  loading  ;  and  by  disappear- 
ing gun-carriages  it  is  but  little  less  so,  being  then 
subject  only  to  danger  from  shots  on  the  rapidly 
descending  branch  of  their  trajectory.    Let  us  now 


Economic  Value  of  Different  Elements,       59 

introduce  these  elements  into  the  calculus,  and  de- 
cide how  much  we  can  afford  to  pay  for  such  extra 
protection.  This  may  be  computed,  with  all  needful 
precision,  by  giving  a  coefficient  to  a,  in  the  last 
equation.  Thus,  if  b  denote  the  quotient  of  the  thne 
during  \^hich  the  gun  is  exposed  between  two  conse- 
cutive shots  by  the  whole  time  between  two  conse- 
cutive shots,  h  a,  will  represent  the  mean  area  serv- 
ing as  a  target  ;  and  we  have  only  to  substitute  h  a^ 
for  a^  in  the  above  value  for  M,  giving  for  this  class 
of  gun  protection : 

a  —  ha, 


(^2)  M^ 


ha 


Strictly  speaking,  h  should  be  a  little  less  than  the 
fraction  above  indicated,  because  this  mode  of  mount- 
ing gives  the  power  of  entirely  withdrawing  from 
danger  any  particular  gun  upon  whose  emplacement 
the  enemy  is  concentrating  his  fire,  and,  while  he  is 
thus  wasting  ammunition,  taking  advantage  of  the 
comparative  security  of  our  other  guns  (against 
which  he  must  have  temporarily  reduced  his  fire)  to 
overwhelm  him  with  deliberate  practice.  Since  the 
gun  has  to  be  moved,  however,  this  advantage  will 
probably  be  offset  by  a  small  lengthening  in  the  time 
between  shots— /. 6.,  by  a  small  increase  in  t^,.  Both 
these  details  may  be  neglected,  because  their  differ- 
ence is  too  small  a  quantity  to  be  considered  in  an 
analysis  so  general  as  this. 

In  combining  these  several  elements  into  one  equa- 
tion, it  must  be  remembered  that  the  fractional  co- 
efficients represent  the  maximum  percentages  of  the 
cost  of  the  gun  and  mounting  to  be  economically  ex- 
pended in  the  improvements  which  the  terms  of  the 
formula  represent  ;  and  hence  that  new  coefficients 
must  be  added  to  reduce  the  values  thus  found  to  the 
actual  percentages  necessary  to  secure  the   desired 


60  Economy  in  Coast  Defence, 

improvements.    Let   A  and  B  represent   such   coef- 
ficients, respectively,  and  we  may  write  : 

X  V +  AxV  T-\- BxVM^S 

S 


(3)     x  = 


V  (1  +  A  T+BM) 


Proceeding  to  numerical  applications  of  these  for- 
mulse,  let  us  first  compute  the  largest  price  which  can 
judiciously  be  paid  for  appliances  for  loading  supe- 
rior to  those  available  in  hand-work.  Assuming  t  to 
be  5  minutes,  i,  to  be  10  minutes,  and  t,^  to  be  5  min- 
utes, equation  (1)  indicates : 

y_10-5  _^ 
5 

That  is,  a  sum  equal  to  the  cost  of  the  gun  mount- 
ed  without  cover  for  hand-loading,  or  say  $70  000, 
may  be  expended  to  reduce  the  time  of  loading  from 
10  minutes  to  5  minutes.  The  actual  cost  of  such  im- 
proved facilities  would  not  probably  exceed  $20  000, 
liberally  estimated.  Hence  the  numerical  value  of  A 
(the  quotient  of  20  000  by  70  000)  becomes,  say,  0.3. 

In  discussing  the  question  of  cover,  five  kinds  of 
mounting  will  be  considered:  the  simple  barbette  car- 
riage behind  an  earthen  parapet ;  a  King  disapx)ear- 
ing-carriage  behind  an  earthen  parapet  ;  a  lift  of  the 
pattern  elaborated  by  General  Duane ;  an  armored 
casemate,  and  a  revolving  turret.  To  make  the  com- 
parison exact  it  would  be  necessary  to  know  the  pre- 
cise dimensions  of  the  gun,  of  the  carriage,  and  of  the 
exposure  with  each  kind  of  cover.  I  shall  only  at- 
tempt to  make  use  of  values  closely  approximate  to 
the  truth. 

When  a  12-inch  gun  is  mounted  without  cover 
upon  a  carriage  made  after  the  old  barbette  centre- 
pintle  pattern  for  hand-loading  only,  it  offers  a  tar- 


Economic  Value  of  Different  Elements^,       61 

get  of  about  70  square  feet  to  a  direct  fire  from  the 
front,  and  of  about  175  square  feet  to  a  fire  perpen- 
dicular to  its  flank.  These  areas  are  computed  upon 
the  assumption  that  shots  may  arrive  at  any  angle 
between  the  horizontal  and  a  fall  of  10°;  and,  also, 
that  if  they  pass  2  feet  below  the  level  of  the  traverse- 
rails  they  will  disable  the  gun.  Intentional  ricochet 
fire  is  ignored  as  no  longer  probable,  especially 
against  guns  on  bluffs.  Since  the  fire  may  come 
through  a  wide  arc  in  front,  a  mean  of  the  two  areas 
above  given,  or  125  square  feet,  will  be  assumed  as  a 
fair  value  to  represent  the  target  presented  to  the 
enemy. 

Case  of  a  Non-disappearing  Barbette.— A  shot 
striking  the  superior  slope  in  front  of  the  gun  ten  feet 
or  less  from  the  interior  crest  would  undoubtedly 
disable  the  gun.  The  descending  branch  of  a  trajectory 
having  a  fall  of  ten  degrees,  passing  through  this 
point,  would  intersect  the  platform  near  the  rear  tra- 
verse-wheels. The  protection  afforded  to  the  gun  by 
this  mode  of  mounting  is  tlierefore  much  less  than 
would  appear  at  first  sight.  Indeed,  the  area  of  the 
exposed  target,  computed  upon  the  assumptions 
above  made  for  the  unprotected  gun,  has  still  the 
large  value  of  about  80  square  feet.  Hence,  by  equa- 
tion (2), 

^^125-(1X80)^0.56 
1X80 

Hence  $70  000x0.56,  or  $39  200,  is  the  maximum 
sum  which  can  economically  be  expended  for  this 
mode  of  mounting.  The  average  actual  cost  of  such 
a  battery  would  probably  not  exceed  $20  000,  show- 
ing that  it  is  judicious  to  give  even  this  insufficient 
protection  to  the  gun.  Indeed,  on  very  high  sites, 
like  the  bluffs  bordering  the  Golden  Gate,  these 
figures  give  an  exaggerated  idea  of  the  defects  of  the 
system. 


62  Economy  in  Coast  Defence, 

The  value  of  B  for  this  kind  of  mounting  (20  000 
divided  by  39  200)  is  0.51. 

Case  of  the  King  Mounting  for  the  50-ton 
13-inch  Rifle. — The  gun  in  its  firing  position  ex- 
poses a  target  of  about  80  square  feet ;  and  in  its  load- 
ing position,  perpendicular  to  the  parapet,  a  target  of 
about  40  square  feet — computed  on  the  same  prin- 
ciples as  above. 

Major  King  estimates  that  the  gun  can  be  fired 
with  steam-power  deliberately  once  in  six  minutes  ; 
but  by  improved  machinery  it  could  doubtless  be 
fired  once  in  five  minutes.  Assume  it  to  be  exposed 
in  the  firing  position  one  minute,  and  in  the  loading 
position  perpendicular  to  the  parapet  four  minutes, 
and  ha,  becomes 

S^^t^X^  ^  48  square  feet. 


And  from  equation  (2)  we  have  : 

^^125-48^1  go 
48 

Hence  $70  000X1. 60=$112  000  is  the  largest  sum 
which  can  be  paid  judiciously  for  this  mode  of  mount- 
ing. The  actual  cost  of  such  a  battery,  including 
the  extra  cost  of  the  carriage,  would  probably  not 
exceed  $25  000.  Hence  the  value  of  B  (25  000  di- 
vided by  112  000)  becomes  0.22. 

Case  of  the  Duane  Lift.— The  gun  in  its  firing 
position  will  expose  a  target  of  about  80  square  feet, 
and  in  its  loading  position  will  be  entirely  covered. 
Assume  it  to  be  fired  once  in  5  minutes,  during  which 
it  is  exposed  2  minutes,  then  ha^  becomes  : 


?^^  =  32  square  feet. 


Economic  Value  of  Different  Elements.        63 

And  from  equation  (2)  we  have  :  • 

Jf=l^ii:??  =  say  2.90 

Hence  $70  000x2. 9=$203  000  is  the  maximum 
which  should  be  expended  for  this  mounting.  The 
actual  extra  outlay  is  estimated  at  about  $80  000 ; 
and  the  value  of  B  (80  000  divided  by  203  000)  be  • 
comes  0.40. 

Case  of  au  Armored  Casemate.— The  gun  is 
constantly  exposed,  forming  a  target  which  may  be 
estimated  at  20  square  feet.    Hence  from  equation  (2) : 

M=.  ^^^~  ^^  c=  say  5.25 
20  ^ 

Hence  $70  000x5.25=$367  500  is  the  maximum 
judicious  outlay.  The  actual  extra  cost  of  such  a 
mounting  will  probably  be  $200  000.  Hence  for  B 
(200  000  divided  by  367  500)  we  have  0.55. 

Case  of  a  Revolving  Turret.  —The  gun  will  ex- 
pose a  target  of  about  20  square  feet,  for,  say,  two 
minutes  out  of  five.     Hence 

5« -20X2^8. 


and  from  equation  (2)  we  have  : 


M=- 1^5^!^  =:  say  14.62 

8 

Hence  $70  000x14.62^$!  023  400  is  the  maximum 
price  which  should  be  paid  for  this  mounting.  But 
the  actual  extra  cost  would  probably  nearly  or  quite 
equal  this  sum,  and  B  is  therefore  unity. 

General  Conclusions.— Equation  (3)  solved  with 
these  values  exhibits  the  comparative  results  (shown 
in  the  following  table)  of  the  expenditure  of  one  mil- 
lion dollars  for  providing  12-incli  50-ton  rifles.  The 
figures  in  the  second  column  show  the  number  of 
guns,  firing  once  in  five  minutes  and  mounted  as  de- 


64 


Economy  in  Coast  Defence. 


signaled  in  the  first  column,  which  can  economically 
be  placed  in  position  ;  and  the  figures  in  the  third 
column,  the  number  of  such  guns  which  can  actually 
be  mounted.  The  fourth  column  gives  the  number  of 
shots  which  can  be  fired  per  hour  by  the  number  of 
guns  indicated  in  the  third  column.  The  fifth  column 
exhibits  the  relative  life  accorded  by  the  different 
mountings,  assumed  to  be  measured  by  the  inverse 
ratio  of  their  exposures.  The  sixth  column  contains 
the  quotients  of  the  products  of  the  figures  in  the 
fourth  and  fifth  columns  by  that  product  for  the 
guns  mounted  with  ''no  cover,  hand-loaded."  These 
quotients  perhaps  exhibit,  as  correctly  as  such  an  ap- 
proximate analysis  permits,  the  economic  merit  of 
the  investments — upon  the  supposition  that  the  en- 
gagement is  to  last  long  enough  to  make  the  theory 
of  probabilities  applicable.  Local  conditions  may 
materially  modify  the  figures. 

ECONOMIC  COMPARISON  OF  DIFFERENT  MOUNTINGS. 


MOUNTING. 


No  cover,  hand-loaded 

Simple  barbette 

King  disappearing...-. 

Duane  lift 

Armored  casemate 

Revolving  turret 


NUMBER  OF  12-INCH  50-TON  GUNS  IN  POSITION 
FOR  $1  000  000. 


7.7 
4.9 
3.4 
2.2 
1.0 


14.0 
9.0 
8.7 
5.9 
3.4 
1.0 


84 
108 
104 
71 
41 
12 


1.0 

1.6 
2.6 
4.0 
6.2 
15.6 


1.0 
2.1 
3.2 
3.4 
3.0 
2.2 


Economic  Value  of  Different  Elements.       65 

From  this  point  of  view  it  would  appear  that  the 
Duane  lift  and  the  King  disappearing  carriage  offer 
the  largest  return  for  funds  invested  in  mounting 
50-ton  guns.  King's  old-model  carriage,  mounting  a 
25-ton  15-inch  Rodman  gun,  was  thoroughly  tested, 
and  was  successful ;  and  there  is  no  doubt  that  his 
improved  pattern,  designed  for  larger  guns,  should 
be  experimented  with  at  once. 

This  comparison  as  applied  to  the  revolving  turret 
requires  qualification.  For  sea-coast  use  they  can  be 
and  usually  are  made  to  contain  two  guns,  because 
this  involves  less  cost  per  gun  than  when  only  one  is 
thus  mounted.  Moreover,  sea- coast  turrets  are  not 
favored  for  guns  of  so  small  weight  as  50  tons.  The 
table,  therefore,  must  not  be  taken  to  imply  more 
than  it  actually  expresses.  Upon  the  basis  of  the 
above  computation,  a  much  more  favorable  result 
than  appears  above  would  be  shown  for  mounting 
two  110-ton  guns  in  a  single  turret. 

It  will  be  noted  that  the  moral  effect  of  the  pro- 
tection, real  or  fancied,  afforded  by  cover  in  front  is 
left  to  be  taken  into  account  by  coefficients  to  the 
sixth  column  of  the  table,  based  on  individual  judg- 
ment. It  is  safe  to  assume  that  guns  mounted  in  the 
open  would  be  deserted  under  the  fire  of  a  modern 
fleet  long  before  they  could  be  dismounted.  Men  be- 
hind a  parapet  which  conceals  the  enemy  feel  com- 
paratively safe ;  and,  by  the  doctrine  of  chances, 
considerable  time  will  elapse  before  a  shot  striking 
where  the  cover  is  weak  disabuses  them  of  the  belief 
in  its  efficiency.  At  the  siege  of  Petersburg  the 
two  lines  were  within  murderous  musketry  range  of 
each  other,  and  rope  mantelets  to  cover  the  gun-em- 
brasures were  a  necessity.  The  first  pattern  was 
bullet-proof,  but  too  heavy  for  convenience,  weighing 
over  500  pounds.  Subsequently  a  lighter  pattern 
which  would  not  certainly  stop  bullets  was  used.     It 


66  Economy  in  Coast  Defence, 

served  all  purposes.  The  enemy  rarely  fired  at  them, 
believing  that  the  shots  would  be  thrown  away  ;  and 
our  men  were  as  happy  behind  them  as  they  had 
been  when  perfectly  protected.  War,  like  all  things 
human,  has  its  successful  shams,  and  cover  more 
apparent  than  real  is  often  valuable. 


Third  Lecture, 


SELECTING  THE  SITE— HOEIZONTAL  FIRE. 

Sites  to  prevent  bombardment  or  to  cover  anchorages — Sites  to  prevent 
a  forced  passage ;  height  and  character  of  the  position ;  development 
of  front  ;  submarine  mine  requirements — Horizontal  fire  ;  range 
and  position-finders;  revolving  turrets;  armored  casemates;  lifts; 
disappearing-gun  batteries;  non-disappearing-gun  batteries;  fiank- 
ing  guns  for  mined  zones ;  magazines. 

With  American  engineers  tlie  objects  sought  in 
preparing  works  of  coast  defence  are  :  (1)  to  forbid 
distant  bombardment;  (2)  to  control  important  an- 
chorages ;  and  (3),  by  far  the  most  common  and  the 
most  urgent,  to  close  important  channels.  Descents 
in  force  are  little  to  be  feared,  and  of  outlying  coal- 
ing stations  we  have  none. 

The  elements  of  a  first  class  system  for  Coast 
Defence,  as  already  stated,  are :  (1)  high-power  guns 
and  mortars  for  keeping  the  armored  ships  of  the 
enemy  at  a  distance ;  (2)  land  fortifications  to  liold 
the  position  ;  (3)  obstructions  in  the  channels  of 
approach ;  (4)  flanking  guns,  movable  torpedoes,  and 
the  electric  light  to  cover  the  obstructions  ;  (5)  vi- 
dette  and  torpedo  boats  to  watch  the  enemy  and 
make  offensive  returns.  These  elements  are  of  pri- 
mary importance,  and  they  are  the  only  elements 
which  can  be  so  regarded  ;  their  relative  importance 
at  different  sites  will  vary,  but,  according  to  modern 
engineering  principles,  no  site  is  thoroughly  defended 
unless  all  of  them  are  represented. 

These  elements  hardly  admit  of  intercomparison 
as  to  relative  importance.  Each  must  be  sufficiently 
elaborate  to  fulfil  its  special  function  at  the  locality. 


68  Selecting  the  Site, 

Thus,  obstructions  cannot  replace  Mgh-power  guns  ; 
neither  can  high-power  guns  replace  flanking  guns  ; 
nor  can  any  or  all  of  them  replace  fortifications, 
or  vidette  and  torpedo  boats,  which  are  essential  to 
guard  against  surprise  and  to  make  the  offensive  re- 
turns so  necessary  to  any  defence  in  war.  When 
these  five  elements  are  judiciously  combined  and 
sufficiently  developed,  they  may  be  trusted  to  do 
their  work  without  further  assistance,  provided  the 
site  is  favorable. 

Considerable  latitude  is  allowed  in  the  composi- 
tion of  these  elements. 

Thus,  obstructions  may  consist  of  electrical  buoy- 
ant or  ground  mines,  self-acting  mines  not  under  con- 
trol, floating  barricades,  sunken  hulks  and  piling, 
or  sometimes  even  imaginary  obstacles  believed  to  be 
real  by  the  enemy. 

The  high-power  guns  required  are  not  the  same  at 
different  localities ;  as  a  general  rule  their  power 
need  not  much  exceed  what  the  draught  of  water  per- 
mits to  be  brought  against  them,  and  they  may  be 
mounted,  according  to  circumstances,  in  armored 
turrets,  in  armored  casemates,  on  lifts,  on  disappear- 
ing carriages,  or  sometimes  even  in  open  barbette. 
Mortars  in  pits  will  be  largely  used. 

A  good  flanking  fire  may  often  be  had  from  8-inch 
or  10-inch  smooth-bore  guns  firing  canister,  grape, 
shrapnel,  and  shells;  but  machine  guns,  and  even  low- 
power  rifled  cannon,  may  play  an  important  part. 
Movable  torpedoes  under  control  from  the  shore  and 
the  electric  light  also  fall  under  this  class. 

Our  cavalry  of  the  sea  will  certainly  comprise  fast 
torpedo-boats,  and  not  impossibly  submarine  boats  of 
the  Nordenfelt  class  ;  while  it  goes  without  saying 
that  such  ships  of  war  as  can  be  spared  from  their 
more  important  and  more  legitimate  field  of  duty 
will  add  powerfully  to  the  defence. 


Sites  to  Prevent  Bombardment.  69 

Evidently  a  modein  fortified  position  on  the  coast 
is  like  an  organ  with  many  pipes  and  stops  ;  and  to 
produce  harmony,  care  and  good  judgment  in  the 
setting-up  and  skill  on  the  part  of  the  player  are  re- 
quired.    We  have  now  to  deal  with  the  setting-up. 

Having,  by  applying  the  principles  enunciated  in 
former  lectures,  formed  definite  ideas  as  to  the  stra- 
tegic importance  of  the  works  and  as  to  the  scale 
upon  which  they  are  to  be  constructed,  the  first  duty 
of  the  Engineer  is  to  select  the  site.  This  requires  a 
thorough  understanding  of  the  fiYQ  elements  in  their 
various  forms,  and  a  practical  knowledge  of  their 
several  requirements  for  efficient  service. 

In  actual  practice  nature  often  leaves  but  little 
choice  in  fixing  upon  the  best  site;  but  in  a  theoretical 
consideration  of  the  subject  it  is  well  to  decide  what  is 
desirable  in  this  connection.  The  object  is  to  prepare 
a  field  of  battle  in  advance  where  our  guns  shall 
overpower  anything  the  enemy  can  bring  against  us  ; 
where  they  shall  be  placed  in  position  in  a  manner 
to  combine  maximum  offensive  power  with  minimum 
vulnerability;  where  the  channel  shall  be  unfavorable 
for  manoeuvres  and  easy  to  obstruct ;  and,  in  a  word, 
where  we  shall  have,  every  advantage. 

SITES  TO  PREVENT  BOMBARDMENT  OR  COVER  ANCHOR- 
AGES. 

Unquestionably  a  primary  object  in  view  is  to  se- 
cure the  place  to  be  defended  against  distant  bom- 
bardment, which,  so  long  as  the  enemy  is  kept  out- 
side the  barrier  erected  in  his  path,  is  his  natural 
mode  of  attack.  At  some  places  situated  on  great 
rivers  or  in  deep  indentations  of  the  coast — as,  for 
example,  at  New  Orleans,  at  Philadelphia,  at  Balti- 
more, and  at  Washington— this  problem  is  easy  ;  at 
others— as,  for  example,  at  the  Naval  Depot  formerly 
projected  at   the  Dry  Tortugas,   which  is   situated 


70  Selecting  the  Site, 

upon  a  small  island  surrounded  by  a  narroAV  cordon 
of  sand-keys  and  coral-reefs,  outside  of  which  tlie 
enemy  could  deploy  and  maintain  tlirougli  an  arc  of 
360°  a  concentrated  lire  at  easy  ranges — the  problem 
to-day  admits  of  no  solution,  and  the  project  lias  been 
abandoned.  Between  these  extreme  conditions  we 
have  many  harbors  which  must  be  defended,  and  the 
question  arises  in  each  case  what  kind  and  amount  of 
tire  mxust  be  j)rovided,  and  what  other  means  may  be 
employed  to  convince  the  naval  commander  that  he 
has  more  to  lose  than  to  gain  from  the  contingent  ad- 
vantage of  shelling  the  port  at  long  range.  This  prob- 
lem involves  :  (1)  the  effective  range  of  modern  high- 
power  guns  mounted  on  shipboard  ;  (2)  the  amount 
of  damage  they  will  probably  inflict  upon  the  port  in 
question  ;  and  (3)  what  kind  and  amount  of  land-fire 
and  what  other  expedients  will  best  produce  the  de- 
sired conviction  that  bombardment  is  inexpedient. 
Each  of  these  questions  admits  of  diJ3ferences  of 
opinion,  and  I  can  only  give  my  own. 

I.  As  to  the  extreme  ranges  to  be  expected  from 
naval  guns,  I  assume,  with  Lieut.  Very  and  others, 
that  from  13°  to  15°  is  the  maximum  practicable  ele- 
vation for  guns  on  shipboard.  At  14°  Krupp's  30,5- 
centimetre  gun,  35  calibres  long,  has  thrown  its  pro- 
jectile about  6.5  miles.  Without  entering  into  a  dis- 
cussion of  the  subject,  which  in  this  company  would 
be  travelling  over  familiar  ground,  I  will  state  that 
as  an  engineer  officer  I  have  little  expectation  that 
bombardment  from  shipboard  will  ever  be  seriously 
attempted  at  ranges  exceeding  six  or  possibly  seven 
miles  ;  and  bearing  in  mind  the  tremendous  shock 
upon  the  deck  which  cannot  be  avoided  in  such  prac- 
tice, the  immense  number  of  shots  required  for  ef- 
fective work  where  the  results  cannot  be  accurately 
noted,  and  the  short  life  even  of  the  best  modern 
high-power  guns,  I  do  not  believe  that  we  have  much 


Sites  to  Present  Bomhardment  71 

to  fear  at  so  long  ranges,  or,  indeed,  at  ranges  consid- 
erably less  than  those  named.  That  these  views  are 
entertained  abroad  is  sufficiently  shown  by  the  dis- 
cussion of  the  problem  for  Spezzia.,  mentioned  in  a 
former  lecture,  where  the  engineers  considered  4.6 
miles  as  sufficient  to  secure  even  their  chief  naval 
establishment  against  unendurable  annoyance. 

Even  in  conservative  England  the  dangers  of  bom- 
bardment at  panic  ranges  are  discounted.  Colonel 
Schaw,  R.E.,  the  well-known  Deputy  Director  of 
AVorks  for  Fortification,  said,  in  a  lecture  delivered  be- 
fore the  Royal  United  Service  Institution  less  than  a 
year  ago :  "  Bombardments  are  now  possible  at  ranges 
of  8  000  to  10  000  yards  distance,  which  would  have 
seemed  fabulous  in  former  days ;  and  although  the 
actual  destruction  produced  by  a  bombardment  may 
be  less  than  would  be  at  first  siglit  thought  probable, 
yet,  if  ammunition  be  plentiful,  it  is  undoubtedly 
very  serious,  and  may  be  disastrous  if  magazines  be 
exploded  or  important  storehouses  set  on  fire. 

^^  Dockyards  are  perhaps  less  inflammable  now 
than  they  were  in  former  days,  as  iron  enters  so 
largely  into  the  construction  of  ou^  ships  ;  yet  a  great 
quantity  of  wood  and  otlier  materials  that  can  be  set 
on  fire  must  be  found  in  every  dockyard,  and,  in  any 
case,  the  bursting  of  large  shells  containing  many 
pounds  of  powder,  or  perhaps  dynamite,  will  work 
great  havoc." 

It  will  be  noticed  that  he  limits  the  dangerous 
range  to  from  8  000  to  10  000  yards— ^^^.,  from  4.5  to 
6.0  miles. 

In  the  discussion  which  followed  the  reading  of 
the  paper,  Captain  Henderson,  Royal  ISTavy,  made 
use  of  the  following  language:  ^'I  doubt  the  effi- 
ciency of  bombardment  at  long  ranges  by  ships  under 
way  (for  ships  cannot  anchor  for  this  purpose  if  ex- 
posed to  gun-fire  or  Whitehead  attack),  against  uii- 


72  Selecting  the  Site, 

seen  objects,  without  any  knowledge  of  the  damage 
done  ;  for  the  sliort  life  of  breech-loadiiig  heavy  rilled 
guns  necessitates  every  shot  being  carefully  hus- 
banded." No  speaker  criticised  this  conclusion  or 
suggested  a  longer  range  as  dangerous.  Like  contin- 
uous picket-liriug  on  the  lines  of  an  army,  the  re- 
sults will  not  compensate  the  outlay,  for  reasons  in- 
dependent of  the  ballistic  power  of  the  guns. 

II.  As  to  the  damage  which  can  be  iniiicted  at 
these  extreme  ranges,  experience  at  Charleston, 
Yicksburg,  Petersburg,  and  even  Paris,  has  slio\^n 
that  many  siege  projectiles  may  fall  within  the  limits 
of  a  city  without  compelling  a  surrender.  The  laiger 
sizes  of  naval  shells  will  produce  more  destructive 
results,  and,  among  buildings  like  those  in  the  lower 
part  of  New  York,  they  would  probably  prove  unen- 
durable ;  but  in  a  sparsely  settled  city  like  Galves- 
ton I  should  not  ajpprehend  a  decisive  result. 

III.  As  to  what  expedients  are  best  to  deter  ves- 
sels from  indulging  in  distant  bombardment,  or  to 
cover  important  anchorages,  I  attach  great  importance 
to  a  well-directed  fire  from  many  heavy  mortars,  in 
pits  quite  out  of  sight,  having  a  range  of  5  miles,  and 
so  mounted  as  to  bring  their  fire  perfectly  under  the 
control  of  one  officer.  By  mounting  them  compactly 
on  centre-pintle  carriages,  with  traverse-circles  grad- 
uated to  360°  from  a  common  origin  of  azimuths,  this 
is  easily  accomplished,  as  will  appear  in  the  next 
lecture.  Supplemented  by  outlying  groups  of  de- 
tached mines  to  be  fired  by  judgment,  and  by  a 
swarm  of  fast  torpedo-boats  ready  to  rush  upon  the 
enemy  when  enveloped  by  the  smoke  of  his  own 
gnns,  these  mortars,  I  think,  would  soon  bring  about 
the  desired  frame  of  mind. 

In  fine,  with  proper  arrangements,  I  believe  little 
is  to  be  feared  from  distant  bombardment  when  our 
defensive  works  are  placed  at  six  miles  outside  the 


Sites  to  Prevent  a  Forced  Passage.  73 

object  to  be  defended,  be  it  a  densely  populated  city, 
a  depot,  a  navy-yard,  or  a  port  crowded  with  vessels 
of  commerce.  Still,  if  ten  miles  be  practicable  at  rea- 
sonable expense,  no  engineer  to-day  would  probably 
choose  a  less  distance  for  works  to  prevent  distant 
bombardment. 

SITES   TO   PREVENT  A   FOKCED   PASSAGE. 

In  selecting  a  line  for  blocking  the  entrance,  cer- 
tain local  conditions  are  desirable — snch  are  a  single 
channel,  a  favorable  height  and  character  of  banks, 
a  well-developed  front  for  ourselves,  a  contracted 
front  of  attack,  and  a  channel  easy  to  obstruct ;  the 
latter  calling  for  moderate  depth,  small  tidal  range, 
gentle  curients,  water  sufficiently  turbid  to  conceal 
mines,  and  a  muddy  bottom  to  bury  the  electric 
cables.     Each  wilFbe  considered  in  turn. 

Height  and  Character  of  the  Position. — A 
low  site  near  the  sea- level  possesses  a  single  advan- 
tage over  one  moderately  high — it  favors  ricochet  fire. 
But  in  the  days  of  smooth-bore  guns  and  wooden 
ships  this  was  the  most  effective  kind  of  tire  known, 
because  a  small  error  in  elevation  or  a  variation  in 
strength  of  powder  did  not  prevent  destructive  hits. 
For  this  reason  water-batteries  were  often  placed  at 
the  water's  edge,  even  when  such  locations  involved 
extra  expense  in  foundations.  Fort  Wadsworth,  in 
New  York  Harbor,  is  an  example  in  point. 

With  rifled  guns  this  advantage  has  lost  much  of 
its  value,  even  against  unarmored  ships,  because  after 
striking  the  water  the  projectile  often  diverges  widely 
from  the  plane  of  tire.  Still,  as  many  old  smooth- 
bore guns  will  continue  to  be  used  for  the  flanking  of 
submarine  mines  when  attacked  by  boats,  ricochet 
fire  is  not  entirely  obsolete  even  to-day.  Against 
armored  ships  it  conld  no  longer  be  used,  because 
after  even  one  grazing  impact  on  water  so  much  of 


74  Selecting  tlie  Site, 

the  velocity  is  lost  as  to  destroy  the  effective  energy 
of  the  largest  projectile. 

On  the  other  hand,  a  low  site  for  land  guns  entails 
many  disadvantages.*  (1)  It  affords  no  direct  fire 
upon  the  deck  of  a  ship,  which,  being  her  most  vul- 
nerable point,  should  always  be  attacked.  (2)  It  en- 
ables ships  to  dispense  witli  high  angles  of  fire,  for 
which  the  mode  of  mounting  their  guns  in  a  measure 
disqualifies  them.  (3)  It  places  the  hostile  guns  on 
shipboard  on  an  equality  with  land  guns  as  to  energy 
of  impact — an  advantage  which  nature  denies  them 
in  attacking  a  high  battery.  For  example,  a  16-inch 
rifle,  firing  projectiles  weighing  one  ton  from  a  bluif 
200  feet  high,  will  have  its  efl'ective  energy  of  imx)act 
increased  200  foot-tons  by  gravity — a  matter  worth 
considering  wlien  striking  a'' plunging  blow  upon  a 
3-inch  steel  deck.  A  similar  gun  returning  this  fire 
from  shipboard  will  lose  an  equal  amount  of  energy 
in  the  projectile,  which  must  be  raieed  against  grav- 
ity to  the  top  of  the  bluif  ;  the  ship  will  therefore  be 
handicapped  to  the  extent  of  400  foot-tons  for  every 
shot  jn  a  duel  fought  under  such  conditions.  (4) 
The  depression  of  the  axis  of  the  land  gun  fired  fi'om 
a  high  site  tends  to  make  the  trajectory  more  nearly 
normal  to  the  deck,  while  the  corresj)onding  elevation 
of  the  axis  of  the  gun  on  shipboard  tends,  at  short 
ranges,  to  make  its  trajectory  still  more  oblique  to 
the  parapet,  and  especially  more  oblique  to  inclined 
armor.  (5)  A  high  site  compels  the  ship  to  keep  her- 
self at  a  certain  distance  in  order  to  bring  the  guns 
to  bear,  and  thus  interferes  with  the  precision  of  fire 
needful  to  dismount  land  guns  attacked  from  a  mov- 
ing gun  platform  like  the  deck  of  a  shij).  Even*nt 
Fort  Mex,  a  low  w^ork  at  Alexandria,  out  of  920  shots 
fired  at  14  guns  piactically  en  harhette  by  five  ar- 
mored ships  at  ranges  from  1  000  to  3  800  yards,  two 
land  guns  were  perhaps  grazed  but  none  were  dis- 


Sites  to  Prevent  a  Forced  Passage.  75 

abled  b.v  direct  hits ;  and  only  direct  hits  can  place 
a  gun  properly  mounted  on  a  bluff  Jiors  de  combat. 

These  considerations  make  it  evident  that  where 
nature  has  provided  moderately  high  sites  (say  from 
100  to  200  feet)  they  should  be  occupied  by  the  for- 
tifications of  to-day.  The  question  w^as  not  so  simple 
in  1864,  vs^hen  it  was  brought  seriously  to  the  atten- 
tion of  a  special  Board  of  Engineers  convened,  in 
view-  of  the  tlien  recent  changes  in  guns  and  of  the 
introduction  of  armor,  to  report  what  should  be  done 
in  respect  to  fortifications  under  actual  construction. 
We  were  not  prepared  at  that  date  to  entirely  sacri- 
fice the  advantages  of  ricochet  fire  ;  but  no  data 
existed  to  decide  definitely  how  much  would  be  lost 
by  placing  the  guns  considerably  above  the  water. 

The  problem,  about  this  time,  was  discussed  ana- 
lytically in  a  paper  written  by  Prof.  C.  A.  Schott,  of 
the  Coast  Survey,  at  the  instance  of  General  A.  P. 
Howe,  Inspector  of  Artillery,  IT.  S.  A.,  and  his  re- 
sults were  submitted  by  the  latter  in  a  report  to  the 
Chief  of  Engineers.  Mr.  Schott  based  his  computa- 
tions upon  the  assumption  that  the  angle  of  re- 
bound from  the  water  was  equal  to  the  angle  of 
incidence — an  assumi)tion  which  I  could  not  accept. 
After  the  war  was  over,  in  the  summer  of  1865,  acci- 
dent placed  my  brigade  of  volunteer  artillery  troops 
for  a  short  time  in  the  Defenses  of  Washington  ; 
and  I  took  advantage  of  the  opportunity  to  investi- 
gate the  problem  by  firing  shots  with  15-inch  guns  at 
the  heights  of  36  feet  and  103  feet  above  the  waters  of 
the  Potomac.  These  data  I  subsequently  subjected 
to  mathematical  analysis  ;  and  General  Haskin,  of 
.the  Artillery,  kindly  checked  the  results  by  firing,  in 
1867,  at  Fort  Schuyler,  New  York  Harbor,  with  an 
8-inch  Rodman  gun  and  a  24-pounder,  at  heights 
above  the  water  of  38  feet  and  15  feet  respectively. 
This  investigation  led  to  definite  formulae  and  con- 


76  Selecting  the  Site. 

elusions,  which  are  reported  in  full  in  Professional 
Papers  No.  14  of  the  Corps  of  Engineers. 

Briefly,  the  results  may  be  stated  as  follows  :  Re- 
bounds cease  when  the  angle  of  incidence  increases  to 
about  8  degrees,  whether  fired  from  heights  of  15 
feet  or  103  feet.  The  angles  of  rebound  at  the  first 
and  subsequent  impacts  are  always  greater  than 
those  of  incidence  ;  and  they  follow  a  law  which  was 
experimentally  deduced.  The  loss  in  the  ricochet 
trajectories  of  the  15-inch  gun,  caused  by  increasing 
its  height  above  the  water,  proved  to  be  not  so  great 
as  had  been  imagined.  For  example,  with  spherical 
shells,  weigliing  344  lbs.  and  having  an  initial  veloci- 
ty of  1  166  feet  per  second  (assuming  that  such  projec- 
tiles  are  dangerous  to  unarmored  vessels  when  mov- 
ing with  a  velocity  not  less  than  300  feet  per  second 
at  a  height  above  the  water  not  greater  than  25  feet), 
the  lengths  of  dangerous  ricochet  trajectories  are  as 
follows  : 


HEIGHT  OP  GUN. 

DANGEROUS  TRAJECTORY, 

TOTAL  TRAJECTORY. 

FEET. 

YARDS. 

YARDS. 

10 

3428 

4152 

36 

3122 

4457 

60 

1924 

3758 

104 

821 

2706 

150 

481 

1934 

200 

291 

1508 

250 

63 

1117 

With  residual  velocities  not  less  than  400  feet,  and 
heights  of  projectiles  above  the  water  surface  not 
greater  than  20  feet,  these  figures  become  : 


HEIGHT  OF  GUN. 

DANGEROUS  TRAJECTORY. 

TOTAL  TRAJECTORT. 

FEBT. 

YARDS. 

YARDS. 

10 

3007 

4152 

36 

2311 

4457 

60 

1174 

3758 

104 

433 

2706 

150 

204 

1934 

200 

57 

1508 

250 

50 

1117 

I 


Sites  to  Prevent  a  Forced  Passage.  11 

With  the  smooth-bore  ordnance  in  service  when 
our  i3rovisional  earthen-battery  system  was  phinned, 
it  is  plain  that  a  trajectory  useful  for  ricochet  fire  for 
fully  one-quarter  of  a  mile  was  secured,  even  with 
our  guns  raised  100  feet  above  the  water  ;  and  when- 
ever this  height  was  available  it  tvas  selected  in  locat- 
ing the  works.  We  would  do  the  same,  for  stronger 
reasons,  with  the  ordnance  of  to-day. 

There  are,  of  course,  limits  which  should  not  be 
exceeded  in  raising  guns  above  the  water.  With  a 
depression  of  7°,  which  is  about  the  maximum  pro- 
vided for  by  modern  carriages  and  mountings,  the 
dead  angle  in  front  of  a  gun  200  feet  above  the  water 
would  cover  543  yards  ;  at  400  feet  above  the  water 
this  space  would  be  1  086  yards  wide.  If  a  deep 
channel  past  the  position  lay  within  this  space,  it 
would  evidently  be  necessary  to  place  at  least  part 
of  the  armament  at  a  lower  level. 

The  height  of  the  site  exercises  a  controlling  influ- 
ence upon  die  mode  of  mounting  and  covering  the 
guns.  The  object  sought  is  to  combine  the  widest 
possible  range  and  traverse  with  the  least  risk  of 
being  silenced  by  the  enemy's  Are.  If  the  site  be  low 
and  the  adjacent  water  deep,  the  position  is  very 
unfavorable  and  an  open  barbette  mounting  is  inad- 
missible ;  for  the  ships  would  approach  within  less 
than  1  000  yards,  and  with  shrapnel  and  machine-gun 
lire  would  render  it  impossible  to  serve  the  guns. 
Turrets  for  100-ton  guns  and  casemates  or  lifts  for 
50-ton  guns  are  imperative  for  such  sites.  With 
heights  300  or  400  feet  above  tide  the  conditions  are 
far  more  favorable,  and  open  barbette  batteries  may 
be  constructed  with  reasonable  chances  of  effective 
service.  For  intermediate  heights,  especially  if 
shoal  water  or  mine  fields  prevent  the  near  approach 
of  the  vessels,  disappearing  guns  in  barbette  batteries 
may  be  trusted  to  do  good  service.     On  cliffs  500  feet 


78  Selecting  the  Site. 

high,  like  some  of  those  which  border  the  Golden 
Gate,  land  guns,  however  mounted,  have  enormous 
advantages  :  the  target  is  enlarged  by  the  area  of  the 
deck,  the  fire  is  pluno;ing,  the  enemy  at  short  ranges 
has  difficulty  in  elevating  his  guns,  and  his  shots, 
pass  over  with  little  i'all.  On  the  other  hand,  provi- 
sion must  be  made  to  cover  the  dead  angle  left  near 
the  shore. 

When  a  choice  is  given  between  a  low  site  near 
the  water  and  a  bluff  in  rear,  the  question  of  relative 
cost  will  often  decide  whether  a  more  powerful  gun 
en  barhette  on  the  bluff  or  a  less  powerful  gun  in  a 
more  expensive  form  of  battery  near  the  water  shall 
be  preferred.  Equal  armor-piercing  power  at  a  two- 
mile  range  should  be  secured. 

There  are,  of  course,  other  matters  connected  with 
the  banks  besides  height  which  have  influence  in 
selecting  the  site.  Forests  are  always  advantageous, 
because  they  favor  concealment ;  and  for  mortar  bat- 
teries, from  which  no  sight  of  the  enemy  is  required, 
this  is  so  important  that,  if  not  in  siiu^  trees  will 
often  have  to  be  cultivated.  The  character  of  the  soil 
and  of  the  foundation  ;  the  absence  of  ledges  of  rock, 
which  will  enhance  the  cost  of  construction  ;  and 
many  other  matters  pertaining  to  the  details  of  the 
profession,  must  have  due  consideration,  although 
they  need  not  be  dwelt  upon  here. 

Development  of  Front. — The  batteries  of  the 
defence  should  be  widely  distributed  :  (1)  to  avoid 
accumulations  of  smoke,  which  interfere  with  the 
accurate  firing  demanded  of  modern  guns  ;  this  mat- 
ter is  more  serious  than  formerly  when  far  smaller 
charges  were  burned,  and  when  shorter  ranges  and 
ricochet  tiring  rendered  precision  in  pointing  less  im- 
portant ;  (2)  to  avoid  the  concentration  of  fire  which 
can  be  brought  against  a  contracted  site  ;  shots  aimed 
at  one  gun,  under  such  circumstances,  may  take  effect 


Sites  to  Frenent  a  Forced  Passage.  79 

upon  its  neighbor,  and  bursting  sliells  or  accidental 
explosions  will  cause  the  maximum  of  destruction ; 
(8)  because  a  widely -developed  land  front  favors 
cross-fire,  which  is  exceedingly  effective  upon  some 
types  of  modern  sliijjping,  such,  for  example,  as  that 
of  the  Benbow^  wliere  110-ton  guns  are  exposed  eii 
barbette.  Fighting  "head  on"  maybe  thus  rendered 
impracticable,  except  at  too  long  ranges  to  be  ef- 
fective. 

On  the  other  hand,  in  selecting  the  position  the 
enemy  should  be  forced,  when  possible,  to  make  use 
of  a  contracted  front ;  he  will  thus  not  only  be  sub- 
jected to  the  inconveniences  named  above,  but  also 
may  be  prevented  from  developing  his  full  power, 
and  will  certainly  be  thrown  into  confusion  should 
some  of  his  vessels  become  unmanageable  during  the 
engagement. 

The  map  and  the  ground  should  both  be  studied  with 
a  view  to  selecting  a  site  combining  the  two  advantages 
of  a  wide  development  of  fire  for  ourselves  and  a* 
contracted  front  for  the  enemy.  For  example,  the 
choice  may  lie  between  occupying  projecting  head 
lands  where  our  guns  must  be  massed  on  the  sea- 
shore, and  where  the  enemy  may  develop  his  attack 
from  a  semi-circle,  with  all  his  vessels  advantugeously 
placed ;  or  choosing  an  interior  position  where  our 
guns  may  be  scattered  widely  while  his  front  is  re- 
stricted to  a  narrow  channel.  In  such  cases  the  latter 
site  will  always  be  selected  by  an  engineer.  A  long, 
narrow  gorge  opening  in  rear  into  a  small  bay,  or  a 
sharp  bend  in  the  channel,  will  usually  be  occupied 
by  the  defence  rather  than  a  position  still  farther  to 
the  rear  which  enables  the  enemy  to  deploy  in  the 
bay  or  to  escape  from  a  dangerous  triangle.  The  ap- 
proaches to  Melbourne  present  a  good  example  of  the 
first  class  of  positions;  and  the  East  Kiver  entrance 
to  New  York  harbor,  one  of  the  second.     The  i)osi- 


80  Selecting  the  Site. 

tion  at  the  Narrows  is  a  familiar  illustration  where 
the  natural  conditions  oft'er  great  advantages  to  the 
defence. 

Submarine  Mine  Requirements. — Shallow  wa- 
ter, gentle  currents,  and  small  tidal  range  should 
have  great  weight  in  choosing  a  site  for  blocking  the 
channel,  whether  by  tlie  older  plans  or  by  submarine 
mines,  which  to-day  afford  the  best  and  simplest 
mode  of  so  doing  available  to  the  engineer.  Under 
certain  circumstances  these  conditions  may  of  them- 
selves modify  the  selection  of  the  position  ;  for  where 
the  mines  are,  there  must  also  be  an  array  of  land 
guns  to  cover  them.     San  F'rancisco  is  a  case  in  point. 

This  matter  will  be  rendered  more  clear  by  con- 
sidering briefly  a  few  details.  The  smaller  a  buoyant 
torpedo  is  made,  the  more  easy  it  is  handled  and  the 
more  likely  will  it  be  to  remain  effective  for  a  long 
period.  Even  in  still  water  enough  buoyancy  must 
be  given  to  support  tlie  torx^edo-case,  the  charge,  the 
mooring  ropes,  and  the  electric  cable ;  in  a  strong- 
current  its  depressing  effect  must  also  be  taken  into 
account  or  the  torpedo  will  sink  too  deep  to  be  struck 
by  a  passing  vessel.  With  our  spherical  pattern  tlie 
buoyancy  varies  with  the  cube  of  the  radius,  wliile 
the  great  circle  cross-section  varies  with  the  square 
of  the  radius.  But  the  horizontal  thrust  due  to  the 
current  is  directly  proportional  to  the  great  circle 
cross-section,  and  may  be  estimated  in  pounds  per 
square  foot,  when  applied  to  the  spherical  surface  of 
our  adopted  pattern,  by  taking  one-half  of  the  square 
of  the  velocity  in  feet.  That  is,  a  spherical  torpedo 
32  inches  in  diameter,  having  6  square  feet  of  cross- 
section,  w^hen  moored  in  a  current  of  7  feet  per  sec- 
ond, will  experience  a  horizontal  thrust  of  about 
6  X  ^  X  7' =  147  pounds.  But  this  thrust  is  also  ap- 
plied to  the  mooring  and  electric  cable,  which  in 
water  50  feet  deep  about  doubles  its  intensity — giving 


Bites  to  Prevent  a  Forced  Passage.  81 

in  tills  case  a  horizontal  thrust  of  about  300  pounds 
to  be  overcome  by  buoyancy  additional  to  what  is 
required  in  still  water.  But  to  obtain  increased  buoy- 
ancy sufficient  to  prevent  the  torpedo  from  being 
carried  below  the  draught  of  the  vessel,  its  size  and 
hence  the  above  figures  must  also  be  increased— and 
increased  very  considerably— since  the  gain  varies 
only  as  the  cube  of  the  radius,  while  the  increased 
thrust  varies  as  the  square  of  that  quantity. 

These  figures  give  an  idea  of  the  great  difficulties 
which  beset  the  submarine  miner  wlien  he  has  to  con- 
tend with  a  strong  current.  Great  depths  are  hardly 
less  objectionable;  for  not  only  is  the  increased 
weight  of  mooring  and  cable  (about  one  pound  per 
running  foot)  to.  be  supported,  but  also  the  admissi- 
ble angular  deflection  to  prevemt  too  great  depression 
of  the  torpedo  is  rapidly  reduced,  and  the  absolute 
buoyancy  needful  from  this  cause  is  correspondingly 
increased.  Practically  a  depth  of  100  feet  with  a 
current  of  7  feet  per  second  fixes  the  admissible 
limit  within  which  submarine  mining  is  effective  in 
our  harbors  ;  and  defensive  positions  must  be  chosen 
accordingl}^. 

Excessive  tidal  ranges,  such  as  prevail  in  the 
English  Channel  (20  feet  and  upward),  can  only  be 
overcome  by  a  double  system  of  mines— one  for  low 
water,  and  another  in  rear  of  the  first  for  high  water. 
Very  fortunately  we  are  not  afflicted  with  such  tides 
on  our  coast,  where  10  feet  is  about  the  maximum 
in  any  harbor  of  first-class  importance  ;  hence  this 
double  system  is  not  necessary  in  our  projects  for 
submarine  mines. 

After  duly  considering  these  matters  of  distant 
bombardment,  practicable  height  of  batteries,  nature 
of  the  soil,  development  of  front  for  himself  and 
contraction  of  front  for  the  enemy,  depth  of  water, 
and  the  tidal  range  and  velocities  of  cu/rents  at  the 


82  Selecting  the  Site, 

different  stages,  the  engineer  selects  his  site  or  sites 
and  proceeds  to  study  the  extent  to  be  covered  by  his 
submarine  mines,  the  needful  armament,  and  the  ex- 
act character  and  location  of  his  works. 

HOKIZONTAL   FIKE. 

An  early  matter  for  consideration  is  :  What  sliall 
constitute  the  land  armament  and  how  shall  it  be 
placed  in  i)osition  ?  Tliis  subject  was  referred  by  Con- 
gress for  report  to  a  special  Board,  of  wliich  the  Secre- 
tary of  War,  Judge  Endicott,  was  president— consist- 
ing of  two  officers  of  the  Engineer  Corps  of  tlie 
Army,  two  officers  of  the  Ordnance  Department  of 
the  Army,  two  officers  of  the  line  of  the  Navj^,  and 
two  civilian  experts  in  steel  manufacture. 

This  Board,  in  January,  1886,  endorsing  the  views 
of  the  Board  of  Engineers  and  of  the  last  Armament 
Board  (July,  1884),  recommended,  exclusive  of  old 
guns  now  on  hand,  the  adoption  of  modern  high- 
])Ower  guns  fabricated  entirely  of  steel.  For  the  land 
defence  of  the  twenty-seven  most  important  seaports 
of  the  United  States  the  following  calibies  and  num- 
bers were  specified,  viz. :  44  16-inch  guns,  6  14-inch 
guns,  203  12-inch  guns,  222  10-inch  guns,  102  8-inch 
guns,  4  6-inch  guns,  700  12-inch  rifled  mortars,  and 
24  10-incli  rifled  mortals  ;  also  5  floating  batteries, 
150  toriDedo-boats,  12  special  torpedo-gunboats  for 
the  Lakes,  and  6  161  submarine  mines. 

Summing  up  the  total  new  armament  recom- 
mended for  the  twenty  seven  ports,  we  find  581  guns 
of  all  calibres  and  724  mortars.  The  16-incli  110-ton 
guns  are  recommended  to  be  mounted  in  revolving 
turrets  ;  the  smaller  calibres  in  armored  casements, 
on  lifts,  or  on  disappearing  or  non-disappearing  car- 
riages, according  to  the  peculiarities  of  the  sites.  The 
mortars  are  to  be  served  in  groups  from  pits  entirely 
concealed,  when  practicable,  from  the  enemy's  view. 


Horizontal  Fire.  83 

I  shall  confine  myself  to-day  to  discnssing  the 
different  modes  of  providing  for  the  horizontal  fiie. 

The  power  and  character  of  the  proposed  gnns, 
and  reasons  for  their  selection,  are  so  familiar  to  all 
present  that  time  wonld  be  wasted  in  discussing 
them  ;  but  a  fe\v  words  upon  recent  improvements 
in   land- pointing   will   not  be   out   of  place. 

Range  and  Position  Finders. — The  change 
from  many  small  guns  to  few  large  guns  in  coast 
defence  has  vastly  increased  the  importance  of  mak- 
ing every  shot  tell.  For  this  reason  the  subject  of 
range- finding  has  received  much  study  of  late  years, 
and  many  devices  have  been  presented  for  trial.  For 
sea-coast  works  where  an  altitude  of  not  less  than 
fifty  or  sixty  feet  can  be  obtained,  the  principle 
which  seems  to  lend  itself  best  to  the  requirements 
of  the  problem  is  that  of  ''depression  angles"  :  ix., 
the  angle  is  measured  between  the  horizontal  and  a 
line  drawn  to  the  water- surface  at  the  object  whose 
distance  is  desired ;  this  being  the  parallax  of  the 
known  height  of  the  instrument  above  the  water 
as  seen  from  that  object,  the  distance  may  either 
be  determined  by  calculation  or  be  read  from  a  scale 
on  the  instrument.  The  accuracy  attained  by  some 
of  these  new  devices  is  wonderful.  One  of  the  best, 
known  as  the  Watkin  Depression  Range-Finder,  is 
claimed  to  give  an  error  of  only  about  half  a  dozen 
yards  at  a  range  of  2  000  yards. 

Where  the  site  is  low  the  use  of  horizontal  angles 
becomes  necessary  ;  and  two  observers  at  a  consider- 
able distance  from  each  other,  or  a  very  delicate  and 
costly  instrument  with  a  short  base,  may  be  employ- 
ed, according  to  circumstances. 

But  there  is  another  difficulty  inherent  to  modern 
practice— viz.,  the  volumes  of  smoke  caused  by  burn- 
ing so  large  charges,  which  makes  it  very  desirable 
to  know  more  than  the  simple  distance  to  the  object. 


84  Selecting  tlte  Site. 

This  necessity,  and  the  advantages  which  grow  out  of 
having  one  general  system  of  range-finding  instead  of 
isolated  measurements,  have  led  to  the  introduc- 
tion of  *' position-finders."  These  instruments  de- 
fine the  ship's  exact  position  at  any  instant  of  time  ; 
and  by  having  the  maj)  divided  into  squares  some 
forty  or  fifty  yards  on  the  edge,  and  supplying  lists 
at  the  batteries  giving  the  corresponding  elevation 
and  azimuths,  the  guns,  even  when  completely  shroud- 
ed in  smoke,  may  be  served  with  precision  by  orders 
telegraphed  from  a  distant  station  where  the  fleet  is 
in  view. 

The  first  system  of  position  finding  was  devised 
by  Mr.  Madsen,  and  was  introduced  at  Copenliagen 
in  the  war  of  1864  by  Colonel  Ernst,  of  the  Danish 
Engineers.  It  was  a  complex  system  of  triangula- 
tion  by  theodolites,  under  electrical  control  from  a 
central  station. 

This  plan  was  succeeded  by  the  well-known  Dis- 
tance-Measurer of  Siemens,  by  which,  through  the  aid 
of  electricity,  a  light  arm  is  caused  to  move  over  a 
chart  at  a  distant  station,  always  retaining  its  paral- 
lelism to  the  axis  of  the  governing  telescope.  The 
complexity  of  this  system  and  the  practical  diffi- 
culties attending  it  are  the  chief  objections,  and  they 
apply  to  the  similar  plan  of  Major  Watkin,  R.A., 
submitted  in  1867.  In  all  of  these  three  methods 
the  system  of  corresponding  squares  on  the  chart  and 
on  the  water  forms  the  basis  of  the  operation,  and  it 
is  evident  that  any  well-considered  plan  of  tiiangula- 
tion  can  be  adapted  to  the  same  principle.  Major 
Watkin' s  electrical  position-finder  was  tried  at  Pick- 
lecombe  Battery  in  actual  practice  at  a  moving  tar- 
get, and  with  decided  success. 

When  a  height  of  not  less  than  60  or  80  feet  above 
the  water  can  be  had.  Major  Watkin  has  modified  his 
range-finder  to  give  azimuths  as  well  as  distances  ; 


Horizontal  Fire.  85 

and  llius,  at  a  single  station  wlncli  may  be  far  reniov- 
I^Led  from  smoke  or  hostile  artillery  practice,  tlie  point- 
'^^ing  of  every  gun  in  every  battery  may  be  regulated 
by  ordinary  telegrapliy — the  actual  iiring  may  be  done 
at  the  battery  or  by  electricity  from  the  observing 
station.  This  system  is  now  adopted  in  the  English 
land  service,  and  no  doubt  the  same,  or  something 
imilar,  will  hereafter  be  used  in  all  sea-coast  fort- 
resses. Suitable  stations  are  easily  prei)ared  at  most 
of  our  ports. 

Speaking  of  this  system  before  the  Royal  United 
Service  Institution  within  less  than  a  year,  Colonel 
Schaw,  R.E.,  Deputy  Director  of  Works  for  Fortifi- 
cation, said  :  ''This  sounds  too  complicated  and  sci- 
entific to  be  practicable  ;  but  seeing  is  believing.  The 
S3'stem  is  no  longer  a  project,  but  an  accomplished 
fact,  which  I  have  witnessed  in  successful  operation, 
and  which  I  hope  may  soon  be  applied  to  every  im- 
portant battery  we  possess.  .  .  .  The  percentage  of 
hits  will  be  probably  increased  tenfold." 

Moiiiitiiig  Land  Guns. — Reverting  to  how 
land  guns  should  be  mounted,  it  is  to  be  noted  that 
so  soon  as  a  resort  is  had  to  horizontal  fire  we  are 
compelled  to  face  the  problem  of  how  best  to  en- 
counter the  flying  asteroids  now  to  be  expected  in 
naval  warfare.  Five  principal  plans  are  in  use  to- 
ay — turrets  of  various  types  ;  armored  casemates  ; 
ifts  by  which  the  gun  with  its  platform  complete  is 
raised  to  fire  over  the  parapet,  and  then  lowered  at 
once  for  cover  while  reloading  ;  disappeaiing  car- 
riages operated  in  a  similar  manner  from  a  fixed 
platform,  but  utilizing  the  force  of  recoil  to  raise  the 
gun  ;  and  the  open  barbette  mounting. 

One  remark  is  to  be  made  emphatically  at  the 
outset.  No  matter  what  kind  of  protection  is  chosen, 
some  of  the  defenders  will  be  hurt.  It  appears  to  be 
expected  in  some  quarters  that  the  same  men  who  are 


n 


86  Selecting  the  Site. 

to  be  disciplined  to  endure  the  loss  of  one-tliird  of 
their  numbers  in  serving  a  light  buttery  in  action,  are 
to  be  guaranteed  entire  safet}^  as  to  life  and  linib  in 
serving  the  armament  of  a  sea-coast  fortress.  This 
is  asking  too  much  of  the  engineer,  and  is  raising 
a  false  standard  by  which  to  judge  of  his  work. 
Wh-ere  blows  are  to  be  received  measured  b}^  the  im- 
pact of  the  New  York  obelisk  dropx)ed  from  the  top 
of  Trinity  Church  steeple,  it  is  idle  to  look  for  ab- 
solute security.  Let  us  hope,  before  the  time  comes, 
to  have  in  readiness  works  offering  reasonable 
chances  of  safety  ;  but  if  not,  our  soldiers  may  be 
trusted  not  to  disgrace  the  flag.  If  there  were  no 
risks  to  be  encountered,  the  service  would  cease 
to  be  war  and  soldiers  would  become  mere  laborers. 

Revolving  Turrets. — The  details  of  revolving 
turrets,  with  their  machinery  and  gun-carriages,  are 
so  similar  to  like  arrangements  on  shipboard  that 
time  would  be  wasted  in  discussing  them. 

Land  turrets  are  surrounded  by  a  massive 
masonry  glacis,  below  which,  and  properly  covered, 
are  the  magazines,  the  shell-rooms,  the  engine  and 
boiler  rooms,  the  quarters  for  the  garrison  in  war,  and 
such  store-rooms  for  coal,  etc.,  as  are  necessary  for 
the  service  of  the  guns.  All  these  appurtenances 
may  be  thoroughly  protected ;  and  in  this  resjject 
land  turrets  have  decidedly  the  advantage  over  those 
on  shipboard,  which  must  always  be  liable  to  become 
unserviceable  from  any  seiious  injury  to  the  ship 
itself,  whether  caused  by  a  gun,  by  a  mortar,  by 
a  submarine  mine,  or  even  hy  a  rock  or  shoal. 

On  land  serious  difficulty  is  experienced  in  pre- 
venting fragments,  dislodged  from  the  masonry 
glacis  in  the  near  vicinity  of  the  base  of  the  turret, 
from  becoming  wedged  in  a  manner  to  prevent  its 
rotation.  This  is  attempted  to  be  obviated  in  the 
Dover  turret  by  embedding  in  the  masonry  two  ver- 


I 


Horizontal  Fire.  87 

tical  wroiiglit-iron  plates  parallel  to  each  other,  on 
circumferences  concentric  with  the  turret.  Gruson 
j)rovides  a  massive  glacis  ring  of  chilled  cast-iron, 
buried  in  part  under  the  masonry,  but  curving  to 
the  rear  to  form  half  of  a  roof  of  a  chemin  des  rondes 
passing  around  the  concealed  truss  which  supports 
the  weight  of  the  turret.  The  bottom  surface  of  the 
turret  itself  forms  the  other  half  of  .this  roof.  The 
junction  between  the  two,  near  the  crown  of  the  arch, 
is  well  protected  against  impact  by  the  curved  form 
of  both  parts ;  and  the  space  between  the  plates  is 
too  small  to  admit  fragments  of  stone  large  enough 
to  stop  rotation  against  the  power  of  the  engines. 
This  arrangement  appears  to  be  excellent. 

The  tendency  at  present  is  to  replace  the  cylin- 
drical form  of  turret  by  that  of  a  cupola,  with  curved 
surfaces  inclined  to  the  horizon — the  object  being  to 
break  and  deflect  the  projectiles  by  opposing  only  an 
oblique  surface.  This  form,  admirable  everywhere 
else,  entails  serious  consequences  round  the  embra- 
sures by  the  excessive  cutting  away  of  the  metal 
necessary  to  accommodate  the  gun.  Protection  im- 
mediately over  the  chase  is  certainly  apparent  rather 
than  real ;  and,  worse  still,  the  effect  of  a  very  pow- 
erful blow  upon  the  iron  mass  between  the  two  em- 
brasures, where  it  has  little  or  no  lateral  support, 
becomes,  to  say  the  least,  doubtful;  experiment  here- 
tofore has  thrown  no  light  on  this  difficulty.  In 
these  two  particulars  the  new  form  is  far  inferior  to 
the  old  ;  it  is  the  price  paid  for  the  unquestioned 
advantages  resulting  from  obliquity  of  imx)act.  Un- 
fortunately the  weak  place  falls  immediately  in  front 
of  the  guns,  where  it  can  be  least  favored  by  rapid 
and  skilful  manipulation  of  the  revolving  mechanism.. 
A  shattering  blow  here  could  not  but  be  fatal  to  both 
guns. 

Another  form  of  two-gun  turret,  known  in  Eng- 


88  Selecting  the  Site. 

land  as  the  CoUingwood  mounting,  is  attracting 
attention  for  land  uses.  The  embrasures  of  the  ordi- 
nary turret  are  omitted,  and  the  gun,  mounted  upon 
a  hydro-pneumatic  carriage,  is  lired  in  barbette.  The 
breecli  is  lowered  for  loading,  leaving  the  muzzle 
always  exposed.  The  iiitejior  space  is  covered  with 
a  steel  deck,  with  openings  to  .permit  raising  and 
lowering  the  guns.  In  this  arrangement  rotation  is 
given  by  a  turn-table,  the  heavy  armored  walls  re- 
maining fixed  in  position  ;  they  are  made  of  inclined 
iron  covered  entirely  with  masonry  in  the  form  of  a 
glacis. 

The  question  of  the  kind  of  armor  is  still  an  open 
one  for  land  turrets.  They  have  been  actually  con- 
structed of  wrought  iron  and  of  chilled  cast  iron,  the 
latter  being  now  generally  preferred  on  the  Continent 
of  Europe  ;  they  liave  never  been  made  either  of 
compound  plates  or  of  steel.  The  chief  reason  for 
giving  preference  in  naval  constructions  to  com- 
pound or  steel  armor — less  weight  for  equal  protec- 
tion—loses much  of  its  force  when  applied  to  a 
land  turret.  The  subject  will  be  considered  more 
fully  in  a  subsequent  lecture,  and  I  will  now  simply 
express  my  opinion  that  judgment  in  this  country 
should  be  held  in  suspense  for  the  piesent. 

There  are  serious  objections  to  the  use  of  any 
form  of  turret  in  coast -defence.  They  are  enormous- 
ly expensive ;  they  somewhat  restrict  the  elevation 
of  the  guns  ;  and,  like  all  complex  machines,  they 
are  liable  to  become  unserviceable  in  action  by  a 
single  lucky  shot  which  may  jam  a  gun  in  its  em- 
brasure, or  by  any  chance  accident  to  the  mechanism 
which  may^render  it  impossible  to  revolve  the  turret 
or  to  serve  the  ammunition.  On  the  other  hand,  they 
afford  more  perfect  cover  to  the  guns,  the  personnel, 
and  the  machinery  for  loading  and  pointing  than 
any  other  known  mode  of  protection  ;  they  simplify 


\ 

Horizontal  Fire.  89 

the  carriage  (a  matter  of  no  small  importance  with 
guns  of  this  weight),  since  no  azimuth  motion  aside 
from  that  of  the  turret  itself  is  required  ;  they  afford 
an  all-round  lire  ;  in  the  event  of  an  overpowering 
concentration  upon  a  single  turret  they  permit  all 
vulnerable  parts  to  be  withdrawn  temporarily  from 
action  by  revolving  the  embrasures  to  the  rear  ;  and, 
lastly,  where  nature  has  too  much  restricted  the  area 
of  the  site,  they  compress  into  the  smallest  space  the 
maximum  possible  offensive  power. 

The  balance  between  these  merits  and  demerits 
evidently  becomes  more  favorable  as  the  weight  and 
power  of  the  guns  increase.  In  our  projects  turrets 
are  proposed  only  for  the  16-incli  110-ton  gun,  or  for 
larger  calibres  if  such  should  ever  become  necessary, 
and  for  low  sites  where  a  wide  field  of  fire  is  demand- 
ed. Under  such  conditions  it  must  be  remembered 
that  their  cost,  although  great,  is  less  than  half  of 
the  sums  which  have  been  expended  for  similar  guns 
to  be  brought  against  us  on  armored  ships,  and  less 
even  than  tliat  of  single  buildings  in  our  great  cities, 
which  without  tlieir  protection  may  be  reduced  to 
heaps  of  ruins.  Twenty-two  of  them  were  recom- 
mended by  the  Endicott  Board. 

Armored  Casemates. — This  mode  of  covering 
guns  so  much  restricts  their  field  of  fire  that  it  has 
only  a  limited  application.  About  15  degrees  in 
elevjition  and  60  degrees  in  traverse  (80  on  each  side 
of  the  perpendicular)  are  all  which  can  be  given.  If 
a  larger  traverse  is  demanded,  the  best  way  is  to  in- 
crea,se  the  number  of  guns  and  dispose  them  on  a 
polygon  giving  the  needful  dispersion.  A  hexagon 
is  usually  the  best  form  to  select,  because  all  the 
guns  on  two  adjacent  fronts  can  be  brought  to  bear 
upon  a  vessel  lying  on  the  line  bisecting  the  angle 
included  between  these  fronts.  If  a  polygon  of  a 
greater  number  of  sides  be  selected,  there  will  be  a 


90  Selecting  the  Site. 

wasteful  overlap  of  fire  ;  if  of  a  less  number  of  sides, 
there  will  be  a  dead  angle  which  will  be  taken  advan- 
tage of  by  a  skilful  Naval  Commander — as  was  done 
in  selecting  the  anchorage  for  the  iron-clad  vessels  at 
the  bombardment  of  Fort  Fisher. 

This  kind  of  protection  permits  no  temporary 
withdrawal  of  the  armament  from  action,  either  for 
repairs  or  to  escape  a  concentration  of  hostile  fire ; 
and  this  objection  is  aggravated  by  the  fact  that  per- 
haps no  form  of  battery  is  so  difiicult  to  design  to 
meet  the  conflicting  requirements  of   the  problem. 

The  old  composite  form  of  iron  shields  and  ma- 
sonry merlons  has  long  been  out  of  date.  An  all- 
iron  scarp  is  now  universally  adopted,  with  a  single 
tier  of  guns,  and  with  the  magazines,  etc.,  in  case- 
mates below  them  where  perfect  protection  can  be 
given.  For  low^  sites  this  form  of  battery  affords 
better  cover  than  any  other  except  turrets.  The  cost 
is  materially  reduced  by  combining  several  guns  in 
the  same  battery  ;  it  is  usual  to  consider  from  three 
to  five  as  the  minimum  number.  They  are  necessarily 
crowded  in  a  small  space,  and  the  annoyance  of 
smoke  in  preventing  accurate  aim  may  well  be  feared. 
The  question  of  the  kind  of  armor  to  be  nsed  is  the 
same  as  for  turrets.  It  is  still  an  open  one  in  our 
service. 

Until  the  dimensions  of  gun  and  carriage  are  defi- 
nitely determined  it  is  impossible  to  form  precise 
rules  for  the  interior  space  needful  in  a  casemate.  A 
sufficiently  close  approximation  for  all  general  pur- 
poses may  be  had,  however,  from  the  English  rule, 
which  is  based  on  large  experience  wath  modern  guns 
and  iron  structures.  It  is  in  substance  the  follow- 
ing :  Strike  an  arc  from  the  pintle  as  a  centre,  with 
a  radius  of  24.5  feet ;  the  space  included  between  the 
extreme  lines  of  fire,  with  four  feet  beyond  them, 
will  afford  enough  floor  space  for  any  gun  np  to  the 


Horizontal  Fire,  91 


S12.5-mcli  of  38  tons.  The  12-inch  43-ton  B.  L.  gun 
requires  a  radius  of  ^'o.^  feet,  and  one  of  28.5  feet  is 
favored.     A  clear  height  of  9  feet  is  sufficient. 

Casemate  magazines  are  usually  now  placed  in  a 
second  tier  under  the  guns,  fitted  with  suitable  lifts 
for  supplying  ammunition.  These  lifts  should  be 
placed  in  the  rear  piers,  enlarged  slightly  for  the 
purpose,  where  danger  of  accidental  explosions  com- 
municating to  the  magazines  below  is  at  a  minimum, 
and  where  the  space  required  for  serving  the  guns 
is  not  encroached  upon. 

Reducing  the  size  of  the  gun  makes  comparative- 
ly little  difference  in  the  cost  of  the  casemate,  which 
is  chiefly  dependent  upon  the  size  of  the  armament 
to  be  brought  against  it.  Hence  only  one  type, 
suited  to  the  12-inch  50- ton  gun,  is  proposed  for  our 
service,  and  it  is  restricted  to  low  sites.  Casemates 
for  eighty  of  these  guns  were  recommended  by  the 
Endicott  Board. 

Lifts. — This  class  of  mounting  dispenses  with  the 
use  of  armor  entirely,  or  at  any  rate  restricts  its  use 
to  a  light  bomb  proof  roofing  which  ma}^  be  sometimes 
used  to  stop  fragments  of  shells  and  shrapnel-balls. 
The  gun  and  its  platform  are  placed  behind  a  suita^ble 
parapet,  and  by  hydraulic  power,  with  or  without  the 
aid  of  counterpoises,  are  raised  and  lowered  at  plea- 
sure. When  in  the  firing  position  the  gnn  has  all  the 
capacity  as  to  elevation  and  traverse  afforded  by  the 
best  barbette  carriage,  even,  if  necessary,  being  given 
a  traverse  of  360  degrees;  but  no  sooner  is  its  work 
done  than  it  sinks  out  of  sight  and  is  loaded,  so 
far  as  horizontal  fire  is  concerned,  in  perfect  safety. 

Guns  have  been  actually  mounted  upon  this  prin- 
ciple for  several  years  at  Cronstadt  and  at  Alexan- 
dria ;  and  the  Temeraire  and  other  armored  vessels 
carry  guns  disposed  in  a  similar  manner.  General 
Duane,  when  president  of  the  Board  of  Engineers, 


92  Selecting  the  Site. 

gave  careful  study  to  the  subject,  and  devised  two 
types,  one  v^rith  and  the  other  without  counterpoises, 
which  met  with  such  favor  before  tlie  Endicott  Board 
that  tlie  construction  of  54  of  them  was  recommended 
for  the  defence  of  the  Coast. 

Lifts  are  usually  restricted  to  the  mounting*  of  the 
12- inch  50- ton  gun,  and  are  preferred  for  medium 
heights  where  a  wide  traverse  is  required.  They 
would  serve  an  excellent  purpose  as  the  chief  defence 
of  secondary  ports  where  the  depth  of  water  in  the 
channel  will  not  permit  the  entrance  of  vessels  carry- 
ing a  more  powerful  armament  than  the  12-inch  gun. 
The  cost  is  estimated  at  $100  000  per  gun,  and  it  is 
greatly  to  be  desired  that  the  construction  of  one  of 
them  should  at  once  be  undertaken,  to  enable  the 
minor  details  to  be  perfected  by  trial. 

This  mode  of  mounting  x>ossesses  so  many  and 
such  incontestable  merits  that  a  few  details  may 
prove  interesting.  The  two  types  devised  by  Gene- 
ral Duane  differ  only  in  the  mode  of  applying  power 
to  the  raising  and  lowering  of  the  platform.  They 
have  in  common  a  substantial  parapet  to  resist  the 
lire  of  the  heaviest  gun  which  can  be  brought  against 
them  Usually  the  front  of  this  parapet  would  be  of 
earth,  but  near  the  guns  it  must  be  of  massive  ma- 
sonry, presenting  only  a  horizontal  surface  to  the  fire 
of  the  enemy.  The  crest  is  broken  by  semi-circular 
recesses,  50  feet  in  diameter,  to  receive  the  guns, 
which  are  placed  at  a  minimum  distance  of  74  feet 
apart.  The  centres  of  these  semi-circles  are  live  feet 
in  front  of  the  crest,  giving  a  horizontal  angle  of  fire 
of  180  degrees.  The  arrangements  behind  the  para- 
pet dispense  with  the  use  of  traverses — a  very  great 
advantage,  as  their  absence  destroys  the  usual  clue 
to  the  position  of  the  guns.  The  latter  are  mounted 
on  any  form  of  low  centre-pintle  barbette  carriage, 
which  is  supported  by  a  circular  platform  26  feet  in 


Horizontal  Fire.  93 

diameter.  This  platform,  wlieri  in  the  firing  position, 
forms  x>art  of  the  masonry  floor  of  tbe  recess,  the 
reference  being  six  feet  below  the  crest.  This  floor 
extends'  unbroken  to  the  rear  for  50  feet  from  the 
centre  of  motion  of  the  gun.  Covered  by  it  are  two 
tiers  of  casemates  for  magazines,  shell-rooms,  etc.; 
and  in  front  of  them  on  the  side  of  the  gun  is  a  long 
gallery,  parallel  to  the  crest,  for  communications, 
hydraulic  macliiiiery,  etc.  The  circular  platform 
rests  on  a  trussed  staging,  and  can  be  lowered  14  feet 
to  the  loading  position.  The  muzzle  of  the  gun  in 
the  firing  position  extends  well  over  the  crest.  After 
the  recoil,  if  not  already  there,  it  is  traversed  to  the 
front,  where,  within  an  angle  of  60  degrees,  the  floor- 
ing is  cut  away  to  form  a  recess  to  receive  the  muzzle 
in  lowering.  Loading  is  done  from  a  fixed  position, 
tlie  usual  shot-lift  supplying  the  ammunition  in  front 
of  an  hydraulic  rammer  lo  force  it  home  in  the  gun. 

As  already  stated,  the  foregoing  arrangements  are 
common  to  both  of  General  Duane's  devices.  In  one 
of  them  the  gun  platform  is  lowered  and  raised  by 
means  of  six  counterweio-hts  and  an  hydraulic  ac- 
cumulator  which  communicates  by  pipe  with  the 
gun-lift.  The  counterweights  are  connected  by  wire 
ropes,  running  over  drums,  to  the  foot  girders  of  the 
platform  staging.  The  total  weight  of  gun,  platform, 
and  staging  is  greater  than  the  combined  weight  of 
the  counterweights,  causing  the  gun  to  descend  when 
connection  with  the  accumulator  is  turned  off  and  the 
waste-cock  of  the  gun-lift  is  opened.  The  pressure  of 
the  accumulator,  when  transmitted  to  the  ram  of  the 
gun-lift,  is  greater  than  the  preponderance  of  the  gun 
and  staging,  and  will  raise  them  to  the  firing  position. 

The  other  device  is  operated  without  counter- 
weights by  a  more  powerful  hydraulic  ram,  in  the 
manner  usual  to  such  mechanism.  Experiment  is 
needed  to  determine  which  is  the  better  arrangement. 


94  Selecting  the  Site, 

Disappearing  Gun-Batteries. — The  invention 
of  a  (Carriage  which,  without  change  of  level  in  the 
platform,  shall  remove  the  gun  from  sight  when  fired, 
and  by  this  motion  shall  store  up  the  power  need- 
ful to  raise  it  again  when  wanted,  has  long  engaged 
the  attention  of  engineers  as  well  as  of  artillerists. 

The  advantages  of  such  a  mode  of  mounting  are 
great.  (1)  The  gun  is  exposed  to  injury  only  during 
the  firing.  If  overpowered  it  may  remain  under 
cover,  always  ready  to  resume  action  when  the  ene- 
my is  tired  of  throwing  away  his  ammunition.  In  a 
word,  such  a  battery  can  never  be  ''silenced''  until 
the  guns  are  hit.  (2)  The  greater  part  of  the  person- 
nel is  permanently  under  cover,  and  the  casual- 
ties will  consequently  be  few.  (3)  When  guns  are 
mounted  in  this  manner  no  satisfactory  reconnois- 
sance  can  be  made  by  the  enemy.  I  attach  no  little 
importance  to  this  matter,  having  myself  experienced 
a  like  difficulty  in  land  operations.  The  Confederates 
sometimes  withdrew  tlieir  field-guns  from  the  bar- 
bettes, so  that  the  most  careful  scrutiny  gave  no 
information  as  to  the  artillery  fire  to  which  a  charge 
would  be  subjected.  As  soon  as  the  assault  was  de- 
livered, flanking  guns  would  appear  as  if  by  magic, 
and  with  results  far  exceeding  wliat  would  have  been 
accomplished  if  tbeir  position  had  been  known  and 
our  guns  had  been  disposed  accordingly. 

Many  different  disappearing  carriages  have  been 
devised.  No  less  than  favQ  distinct  systems  have 
been  introduced,  but  most  of  them  are  applicable  only 
to  guns  of  small  calibre.  The  Aloncrief  counterj^oise 
carriage  will  only  carry  guns  about  five  tons  in 
weight.  King's  carriage,  which  alone  has  had  a 
practical  trial  in  this  country,  has  proved  itself  suc- 
cessful with  the  15-inch  25-ton  smooth-bore  gun  ;  and 
his  new  adaptation  for  a  12-incli  50-ton  gun  ought  to 
be  experimentally  tested,  without  delay,  in  competi- 


Horizontal  Fire.  95 

tion  with  the  Buffington  and  any  other  device  which 
promises  success.  The  Moncrief  hydro-pnenmatic 
carriage,  the  Rendel  carriage,  tlie  Raskasoff  carriage, 
and  other  types  are  favorably  regarded  abroad. 
Armstrong  now  furnishes  a  disappearing  carriage  for 
guns  70  tons  in  weight. 

The  excessive  length  of  modern  high-power  guns, 
and  the  loading  at  the  breech,  have  increased  the 
difficulty  of  properly  covering  this  type  of  carriage — 
not  only  from  the  greater  weights  to  be  handled, 
but  also  from  the  comparatively  exposed  position  of 
the  cannoniers,  which  is  so  far  removed  from  the 
parapet  that   curved  fire  becomes  annoying. 

A  special  form  of  battery  suited  to  receive  the 
new  King  carriage  has  been  devised  by  the  Board  of 
Engineers.  The  gun  may  be  loaded  from  the  extreme 
rear ;  but  being  exposed  in  that  position  to  shrapnel 
fire,  and  to  shot  descending  at  an  angle  of  ten  or 
more  degrees,  x>rovision  has  been  made»for  revolving 
the  gun  to  a  position  parallel  to  the  crest,  and  there 
loading  it  from  a  j)assage  in  a  bomb-proof  traverse, 
which  contains,  in  sub-casemates,  the  magazines,  shell- 
rooms,  etc.  The  cost  of  this  battery  is  small,  about 
$15  000,  and  its  efficiency  in  positions  of  moderate 
height  will  be  great.  Cover  is  estimated  at  the  rate 
of  70  feet  of  sand,  or  its  equivalent  in  concrete  or 
stone  masonry.  The  gun  is  lowered  8  feet.  In  ex- 
tending the  battery  an  interval  of  124  feet  is  left 
between  guns.  The  traverses  rise  11  feet  above,  and 
the  terreplein  is  12  feet  below  the  level  of  the  crest. 
A  sunken  passage  6  feet  below  the  terreplein  affords 
secure  communications  and  fair  cover  for  men  en- 
gaged in  loading  in  the  open. 

Non-disappearing  Gun-Batteries.— Probabl  y 
new  batteries  of  this  class  will  be  restricted  to  ex- 
ceptionally high  sites,  where  they  will  certainly  be 
troublesome  to  the  enemy.     Simplicity  and  economy 


96  Selecting  the  Site. 

are  their  chief  merits.  The  only  part  of  our  present 
armament  which  could  with  any  chance  of  success 
reply  to  the  fire  of  modern  guns  is  thus  mounted, 
and  most  of  the  batteries  were  constructed  to  admit 
of  the  introduction  of  the  old  King  carriage,  if  de- 
sired. 

It  is  to  be  noted,  however,  that  although  now 
viewed  with  suspicion  from  perhaps  exaggerated  esti- 
mates of  the  efficiency  of  shrapnel  and  of  rapid- 
firing  guns  on  shipboard,  there  are  indications  that 
where  vessels  can  be  kept  at  a  distance  this  mode  of 
mounting  may  again  receive  favor.  Thus  the  French 
have  adopted  a  simple  barbette  mounting  for  the 
heavy  armament  (four  46- ton  guns)  of  the  Admiral 
Dwperre  and  for  other  ships ;  and  the  English  have 
followed  their  example  in  the  Imperieuse^  the  War- 
spite^  and  even  in  the  Benhoio.  Nay,  more,  the 
heaviest  guns  now  mounted  in  English  land  defences 
(the  four  lOQrton  Armstrong  guns  at  Gibraltar  and 
Malta)  are  placed  in  barbette  behind  a  high  jiarapet 
about  100  feet  above  the  water.  They  are  provided, 
however,  with  a  complete  under-cover  system  of 
loading. 

The  change  from  muzzle-loading  to  breech-loading 
lias,  upon  the  whole,  done  much  to  increase  the  effi- 
ciency of  barbette  batteries.  Although  the  cannoniers 
are  stationed  further  from  the  parapet,  and  are  there- 
fore more  exposed  to  curved  tire,  the  gun  itself  is  a 
great  protection  to  them,  especially  at  high  elevations ; 
and  cover  against  small  missiles  is  easily  given  by 
steel  hoods  enveloping  the  breech. 

Flanking  Guns  for  Mined  Zones.— None  of 
the  modern  high-power  guns  are  well  adapted  for  use 
in  flanking,  being  too  heavy  and  too  few  in  number 
to  be  effective  in  such  work.  Machine  and  rapid- 
firing  guns  will  doubtless  play  an  important  part  in 
such  operations,  especially  for  new  works  where  no 


Horizontal  Fire.  97 

flanking  arrangements  now  exist.  Where  old  ma- 
sonry works  are  available,  they  will  be  measurably 
serviceable,  even  with  their  present  armament  (usually 
10-inch  and  8  inch  Rodman  smooth-bores) ;  for  a  heavy 
fire  of  canister,  grape,  shrapnel,  and  shell  is  as 
effective  now  as  it  ever  was  against  launches  and 
small  craft,  which,  if  permitted  to  countermine,  would 
work  the  worst  damage  to  the  mines.  Such  vessels 
abound  in  every  fleet,  and  provision  to  meet  them  is 
to  be  considered  first.  A  few  of  ^the  converted  8-inch 
rifles  now  on  hand,  judiciously  distributed  among  the 
old  forts,  may  prove  serviceable  against  regular 
counterminers. 

Probably  the  idea  will  suggest  itself  to  every  one 
that  to  depend  on  the  old  works  to  cover  the  flank- 
ing guns  of  the  mines  is  to  rest  on  a  broken  reed  ; 
because  they  can  be  so  easily  breeched  from  a  dis- 
tance by  the  fleet,  and  because,  under  such  a  fire,  the' 
cannoniers  would  be  driven  from  the  guns.  But  it 
must  be  remembered  that  countermining  is  most  to 
be  dreaded  at  night,  when  little  can  be  accomplished 
by  distant  fire  ;  and  that  by  day  the  ships,  while  at- 
tempting to  destroy  the  old  works,  will  be  themselves 
subjected  to  the  deliberate  practice  of  the  high-power 
guns.  Experience  leads  me  to  believe  that  a  heavy 
artillery  fire  upon  an  enemy's  field  battery  will  be 
sure  to  compel  a  reply,  and  I  see  no  reason  to  doubt 
that  the  same  is  true  on  shipboard.  Some  of  the 
flanking  guns  would  doubtless  be  placed  liors  de 
Goinhat  by  occasional  shots,  and  sometimes  the  tem- 
porary withdrawal  of  the  cannoniers  will  doubtless 
be  expedient ;  but  whatever  be  the  demerits  of  the 
old  stone  forts,  a  deficiency  in  number  of  guns  is  not 
one  of  them.  They  swarm  on  every  front,  and  par- 
ticularly on  those  not  visible  to  the  enemy  at  a  dis- 
tance, from  which  their  fire  to  flank  the  mines  will 
largely  be  required.     The  problem  to  destroy  at  long 


98  Selecting  tlie  Site. 

ranges  tlie  efficiency  of  every  one  of  scores  of  flank- 
ing guns,  wliile  suffering  from  the  tire  of  higli-power 
guns,  will,  I  think,  be  neither  simple  nor  satisfactory 
to  tlie  attacking  party.  Judging  by  the  precision  of 
lire  shown  at  Alexandria,  the  enemy  will  be  liors  de 
combat  before  it  is  accomplished  ;  and  while  even  a 
few  of  the  guns  can  be  served  liis  fleet  of  launches 
must  remain  idle.  Wliile  fort's  of  this  type  will 
never  be  constructed  in  the  future,  they  can  still  be 
made  use  of  in  the  plan  of  defence  to-day  ;  and  to 
condemn  them  entirely  is,  in  my  judgment,  a  very 
great  mistake. 

Where  new  works  are  to  be  constructed,  wdi ether 
for  the  flanking  of  mines  or  for  repelling  boat  parties 
attempting  to  land,  so  much  use  will  be  made  of  the 
latest  type  of  small  ordnance  that  I  shall  give  a  brief 
summary  of  some  particulars  which  have  an  import- 
ant bearing  on  land  defences,  even  at  the  risk  of  re- 
calling facts  familiar  to  every  one  present. 

The  machine  guns  of  Gatling,  Gardner,  Norden- 
felt,  and  Maxim  usually  fire  bullets  of  0.45  inch  cali- 
bre, although  Nordenfelt  and  Maxim  both  supply 
patterns  firing  1-inch  steel  projectiles.  The  rapidity 
with  which  the  small  calibres  can  be  served  ranges 
from  600  to  1  200  rounds  per  minute;  they  w-ere  de- 
signed to  replace  infantry  fire,  but  are  nov/  regarded 
as  better  suited  for  defending  positions  than  for 
active  field  service.  The  Nordenfelt  and  Maxim  inch 
bolts  were  designed  to  pierce  the  light  armor  of  tor- 
pedo-boats. The.  Maxim  0.45  inch  projectiles  are 
fired  automatically  at  the  rate  of  660  per  minute,  and 
his  inch  bolts  at  the  rate  of  280  per  minute  ;  the  lat- 
ter pierce  an  inch  of  iron  at  100  yards. 

Hotchkiss  revolving  cannon  are  made  of  calibres 
37  mm.  (1-pounder),  of  47  mm.  (3  pounder),  and  of  53 
mm.  (4-pounder).  They  fire  shells  designed  to  replace 
light- artillery  projectiles  up  to  a  range  of  at  least 


Horizontal  Fire.  99 

2  000  yards  (extreme  range  5  000  yards).  Served  at 
full  speed,  the  smaller  calibres  have  attained  a  rate  of 
600  shots  per  minute,  and,  when  aimed,  of  17  shots 
per  minute.  A  special  flank-defence  pattern  (40  mm.) 
is  designed  for  sweeping  ditches.  The  live  barrels 
are  rifled  on  different  pitches,  ranging  from  1  to  6.7 
turns,  which  enables  them  to  distribute  1  f)00  projec- 
tiles per  minute  with  admirable  uniformity  and 
without  change  of  aim,  over  a  space  300  yards  long 
and  50  feet  wide. 

Rapid-firing  hand- loaded  guns  are  especially  de- 
signed for  repelling  the  attacks  of  torpedo-boats, 
and  they  will  play  an  imi:)ortant  part  in  flanking 
mined  zones.  The  Hotchkiss  Company  fabricates 
them  upon  modern  high-power  principles,  82  to  34 
calibres  long.  About  1  200  yards  is  their  fighting 
range,  their  rapidity  of  fire  varying  from  20  to  10 
shots  per  minute,  according  to  the  care  with  which 
they  are  aimed.  Very  gives  the  following  as  their 
steel-penetrating  power  : 

Calibre  37  mm.,  or  1-pounder  :   0.8  inches  at  muzzle  ; 

0.4  inches  at  1  200  yards. 
Calibre  47  mm.,  or  3  pounder  :    1.7  inches  at  muzzle  ; 

0.8  inches  at  1  200  yards. 
Calibre  57  mm.,  or  6-pounder  :    3.5  inches  at  muzzle  ; 

1.75  inches  at  1  200  yards. 
Calibre  ^^  mm.,  or  9-pounder :    4.0  inches  at  muzzle  ; 

2.25  inches  at  1  200  yards. 
Calibre  100  mm.,  or  33-pounder  :  — inches  at  muzzle  ; 

—  inches  at  1  200  yards. 

Iron  penetrations  are  one-third  greater.  These 
guns  all  fire  steel  shells,  common  shells,  shrapnel,  and 
case  or  canister.  The  three  smaller  calibres  have 
non-recoil  mounts,  and  the  others  recoil  mounts  ; 
they  are  also  sometimes  mounted  on  a  miodified  case- 
mate carriage,  or  like  field  artillery. 


100  Selecting  the  Site. 

The  Elswick  Company  is  now  fabricating  a  4.7- 
inch  30- pounder  pattern  which  has  a  muzzle  velocity 
of  1  900  feet  per  second,  and  which  can  be  fired  iit  the 
rate  of  10  shots  per  minute ;  and  designs  for  a  70- 
pounder  have  been  completed.  Should  this  gun  prove 
successful  a  very  important  departure  in  light  can- 
non of  high  power  may  be  at  hand. 

Rapid-firing  guns  are  also  receiving  attention  at 
Essen.  A  15.5-pounder  was  tested  last  February 
which  gave  a  muzzle  velocity  of  1  990  feet  per  second 
and  a  rapidity  of  22  shots  per  minute. 

These  machine  and  rapid-firing  guns  have  all 
come  into  general  use  since  our  civil  war,  but  they 
are  now  universally  adopted.  When  skilfully  ap- 
plied they  will  be  of  great  service  in  meeting  our 
needs  resulting  fiom  widely  distributing  batteries  in 
Coast  Defence. 

Magazines. — Magazines,  of  course,  are  always 
l^laced,  so  far  as  possible,  out  of  sight  of  the  enemy, 
and  where  his  projectiles  cannot  penetrate.  The 
latter  condition  is  far  more  difficult  to  fulfil  than 
formerly,  and  the  problem  often  becomes  perplexing. 
The  Royal  Engineer  rule  a  few  years  ago  required 
18  feet  of  granite  or  other  masonry  ;  but  they  now 
allow  40  feet,  and  Captain  Lewis  states  (1884):  "It  is 
probable  that  for  the  immediate  present  the  40  feet  of 
protection  aimed  at  with  our  magazines  is  sufficient, 
but  it  will  not  be  so  for  long." 

With  turrets,  casemates,  and  lifts,  and  at  con- 
tracted sites,  the  natural  place  for  magazines  is  in 
a  tier  of  casemates  under  the  guns.  They  should  al- 
ways be  buried  under  ground  when  practicable. 

The  usual  rule  for  capacity  is  based  on  having  100 
rounds  of  cartridges  and  100  rounds  of  shell  on  hand, 
and  not  more  than  four  guns  are  allotted  to  one  ser- 
vice magazine. 

In  future  permanent  magazines  no  attempt  will 


Horizontal  Fire,  101 

• 
be  made  to  preserve  the  powder  dry  by  excluding 
moisture  from  the  room.  Experience  has  shown  that 
this  is  impossible  to  accomjjlish  in  many  cases  ;  and, 
moreover,  the  huge  size  of  modern  charges  will  forbid 
their  preparation  at  the  time  of  firing.  The  cart- 
ridges must  be  put  up  in  advance,  and  in  water-proof 
cases  whicli  will  serve  to  keep  them  dry  indefinitely. 

The  necessity  of  precautions  to  prevent  the  acci- 
dental explosion  of  a  cartridge  en  route  to  the  gun 
from  communicating  fire  to  the  magazine,  is  receiving 
attention  abroad.  Safety-traps  in  lifts  and  swinging 
mantelets  in  magazine  passages  are  recommended  ; 
also  that  no  more  wood- work  about  a  cartridge-lift 
than  is  absolutely  necessary  should  be  allowed. 

No  greater  disaster  can  occur  during  a  bombard- 
ment than  the  explosion,  of  a  large  magazine.  Two 
land  batteries  were  silenced  from  this  cause  at  Lissa 
in  1866,  and  two  at  Alexandria  in  1882.  The  sur- 
render of  the  Castle  of  San  Juan  d'Ulloa  to  the 
French  fleet  in  1838  was  due  to  a  like  catastrophe. 
At  the  storming  of  Foit  Fisher,  JS".  C,  in  January, 
1865,  a  shell  from  a  15-inch  naval  gun  reached  and 
crushed  the  plank  sheathing  of  the  large  traverse  ma- 
gazine at  the  principal  salient  near  the  Blakely  rifle  ; 
and  had  the  fuse  done  its  duty  many  lives  lost  in 
the  subsequent  assault  mi^ht  have  been  saved.  It 
is  safe  to  assert  that  provisions  to  prevent  such  acci- 
dents ill  future  will  engage  the  attention  of  the  En- 
gineers of  every  Nation. 


Fourth  Lecture. 

MORTARS  AND  SUBMARINE  MINES. 

Vertical  fire  ;  advantages  of  rifling  ;  carriages  and  platforms  ;  mortar 
batteries  ;  economy  of  mortars— Submarines  mines  ;  general  condi- 
tions ;  attacks  by  daylight  ;  attacks  by  night  or  in  fogs  ;  attempted 
passage  by  force. 

The  introduction  of  armored  ships  of  war,  besides 
increasing  the  calibre  of  land  guns  and  modifying  the 
nature  of  their  carriages,  of  their  mountings,  and  of 
their  cover,  has  brought  into  so  much  greater  promi- 
nence two  old  elements  of  coast  defence  that  it  may 
almost  be  said  to  have  created  them.  I  refer,  of 
course,  to  vertical  fire  and  to  submarine  mines. 
TJiese  modes  of  counter-attack  directly  assail  what  is 
now,  and  what  must  continue  to  be,  the  most  vulner- 
able parts  of  the  ship— her  deck  and  her  bottom. 
They  have  another  peculiar  merit :  their  attack  ad- 
mits of  no  reply  in  kind.  They  are  weapons  which 
cannot  be  used  by  ships  against  forts,  except  mortars 
in  occasional  river  operations  like  the  bombardment 
of  Fort  Jackson,  below  New  Orleans.  With  vertical 
fire,  the  least  roll  of  the  sea  or  the  least  swinging  to 
the  anchor  must  be  fatal  to  anything  like  precision. 

For  these  reasons  I  suppose  a  discussion  of  mor- 
tars and  submarine  mines,  rather  more  elaborate  than 
has  been  given  to  the  use  of  guns,  may  be  of 'interest 
to  Naval  Officers. 

VERTICAL   FIRE. 

For  the  defence  of  our  entire  coast  the  Fortifica- 
tion Board  of  which  Secretary  Endicott  was  presi- 


Vertical  Fire.  103 

dent,  endorsing  the  views  held  by  tlie  Board  of  Engi- 
neers, recommended  581  high-power  guns  of  all  cali- 
bres, and  724  heavy  mortars,  or,  as  they  are  now 
often  called,  rifled  howitzers.  The  proportion  between 
the  number  of  guns  and  mortars  shown  by  these  fig- 
ures differs  so  enormously  from  that  accepted  by  the 
best  authorities  a  quarter  of  a  century  ago,  that  the 
reasons  for  the  change  demand  consideration. 

They  are,  in  brief,  (1)  Because  the  blow  is  struck 
preciselj^  where  armored  protection  is  least  effective, 
and  where  either  shot  or  shell  are  most  destructive  in 
their  effects.  Indeed,  in  their  power  of  encountering 
such  missiles  ships  have  retrograded  since  the  close 
of  the  civil  war,  when  it  was  proposed  to  give  the 
Kalamazoo  a  solid  deck  tliroughout  of  three  inches 
of  wrought  iron  strongly  supported.  Now  the  ten- 
dency seems  to  be  to  sink  the  protected  deck  below 
the  water-line,  and  thus  to  provide  a  shell-trap  where 
the  effect  of  the  explosion  will  be  increased  to  the 
maximum  by  confinement.  In  plunging  fire  the  mor- 
tar trajectory  is  incomparably  more  effective  than 
that  of  cannon.  The  latter,  with  the  gun  at  a  height 
of  100  feet,  attains  an  angle  of  incidence  of  10  degrees 
only  at  a  two-mile  range,  and  at  a  height  of  500  feet 
only  at  a  mile-and-a-lialf  range  ;  and  this  with  low- 
power  guns.  Modern  high-power  guns  have  still 
flatter  trajectories,  and  are  therefore  still  less  fitted 
for  effective  plunging  fire,  (2)  Because  of  the  greatly 
increased  precision  of  modern  vertical  fire  resulting 
from  the  introduction  of  rifling,  from  improved  sys- 
tems of  range-finders,  and  from  a  disposition  and 
mode  of  mounting  which  devolves  the  responsibility 
of  aiming  upon  a  single  officer  stationed  where  he 
can  accurately  watch  the  effect  of  his  shots  and  cor- 
rect errors  as  soon  as  they  occur.  Formerly  this 
responsibility  fell  upon  the  individual  gunnere,  who 
were  often  annoyed  by  smoke  and  confused  by  the 


104  Mortars  and  Submarine  Mines, 

fall  of  projectiles  other  tlian  their  own  around  tlie 
target— a  difficulty  aggravated  by  the  long  time  of 
flight  as  compared  with  tliat  of  guns.  (3)  Because 
vertical  Are  cannot  be  silenced,  even  on  land,  when 
the  mortars  are  properly  covered.  The  artillery  con- 
test at  the  digging  of  the  Dutch  Gap  Canal  on  James 
River  in  1864  is  a  case  in  point.  The  excavation, 
across  a  narrow  neck  between  two  bends,  covered  an 
area  of  30  000  square  feet,  being  500  feet  long  by  60 
feet  wide.  The  bank  opposite  the  upper  end  of  the 
cut,  held  by  the  enemy,  was  low  ;  that  opposite  the 
lower  end,  held  by  ns,  was  a  bluff  j^robably  80  feet 
above  the  water.  Moreover,  a  signal-tower,  120  feet 
high,  on  this  bluff,  gave  an  excellent  opportunity  to 
overlook  the  whole  ground,  the  river  here  being  only 
400  yards  wide.  To  interrupt  the  digging  of  the 
canal,  the  enemy  i)laced  in  front  of  it,  at  ranges  vary- 
ing fi'om  600  to  800  yards,  four  or  Ave  siege-mortars 
in  sunken  batteries  concealed  behind  clumps  of  trees 
and  provided  with  bomb-proof  cover.  Their  lire 
sunk  the  dredge  and  harassed  the  working  par- 
ties ;  and  to  compel  their  silence  became  an  impor- 
tant object.  Seven  siege-mortars  and  five  guns  were 
placed  in  position  near  the  cut,  where  they  had  a 
crossfire  at  short  range;  and  a  skilful  officer.  Cap- 
tain Pierce,  First  Connecticut  Artillery,  fired  about 
4  000  shots,  taking  advantage  of  the  tower  to  direct 
his  aim,  and  of  the  guns  to  prevent  the  Confederate 
cannoniers  fiom  watching  the  effect  of  their  firing. 
He  interfered  with  their  practice,  but  he  could  not 
compel  their  silence.  This  duel,  and  much  other  fir- 
ing at  Petersburg,  convinced  me  that  a  mortar  bat- 
tery, well  placed,  well  constructed,  and  well  served, 
cannot  be  silenced.  If  this  be  true  in  respect  to  a 
land  attack,  how  much  more  true  is  it  in  resx^ect  to 
.a  naval  attack,  where  no  target  is  presented  for 
horizontal  .fire,. and  where  vertical  fire  is  not  to  be 


Vertical  Fire,  105 

feared !  In  fine,  sliips  may  sometimes  compel  the 
silence  of  land  gnns,  but  they  must  endure  vertical 
fire  so  long  as  they  remain  within  range.  (4)  Be- 
cause of  the  relatively  small  cost  of  mortars,  as  com- 
pared with  that  of  guns,  both  for  fabrication  and  for 
cover  against  an  enemy's  fire.  This  advantage  per- 
mits them  to  be  used  in  large  numbers  without  exor- 
bitant demands  upon  the  Treasury.  Some  of  these 
points  will  bear  elaboration. 

Advantages  of  Rifling. — The  trajectory  of  pro- 
jectiles fired  under  high  angles  differs  materially 
from  that  of  ordinary  gun  practice  ;  and  to  appreci- 
ate the  effect  of  rifiing  mortars  this  difference  must  be 
understood.  Fired  with  an  elevation  of,  say,  45  de- 
grees, the  shell  receives  an  initial  velocity  which  can 
be  resolved  into  two  equal  components,  one  horizon- 
tal and  the  other  vertical.  Both  components  will  be 
gradually  reduced  by  the  resistance  of  the  air  (acting 
nearly  in  proportion  to  their  squares),  but  the  ver- 
tical component  is  also  directly  opposed  by  gravity, 
which  soon  brings  it  to  zero.  This  will  occur  near 
the  highest  point  of  the  trajectory.  Gravity,  still 
acting,  will  then  communicate  a  velocity  in  the  reverse 
direction,  which  will  increase  proportionately  to  the 
square  roots  of  the  distances  passed  over,  until  the  re 
sistance  of  the  air,  making  itself  felt  more  and  more, 
will  at  last  establish  an  equilibrium,  and  the  compo- 
nent will  become  unvarying.  The  name  "final  ve- 
locity" is  usually  applied  to  this,  the  maximum 
theoretical  velocity  which  can  be  used  against  a  ship. 
Unfortunately,  from  an  engineer  point  of  view,  its 
value  is  not  great,  being  for  a  10-inch  round  shot, 
580  feet ;  for  a  15-inch  round  shot,  700  feet ;  and  for  a 
20  inch  round  shot,  790  feet.  These  values  are  theo- 
retical limits  which  can  never  be  reached,  although 
they  may  be  approached  in  long-range  practice. 

The  vertical  component  has  so  small  an  average 


106  Mortars  and  Submarine  Mines. 

value  that,  within  the  limits  of  ordinary  firing,  the  laws 
applicable  in  vacuo  give  results  differing  but  slightly 
from  exact  accuracy.  Hence,  within  these  limits,  the 
vertical  velocity  of  impact  of  a  mortar  projectile  may 
be  assumed  to  be  that  which  would  be  acquired  by  a 
heavy  body  falling  in  vacuo  a  height  equal  to  one- 
fourth  of  the  horizontal  range  in  feet.  At  elevations 
above  45  degrees,  the  charge  remaining  the  same,  the 
height  attained  is  greater  and  the  range  is  less  ;  and 
hence,  in  obtaining  a  given  range^  the  useful  compo- 
nent of  the  velocity  is  doubly  increased.  At  60  de- 
grees elevation  the  height  is  one-half  greater  and  the 
range  is  one-tenth  less,  and  at  75  degrees  elevation 
the  height  is  four-fifths  greater  and  the  range  one- half 
less  than  at  45  degrees. 

From  these  well-known  laws  thefollowing  approx- 
imate rules  result  for  estimating  the  vertical  velocity 
(in  feet  j)er  second)  of  mortar  projectiles  at  impact, 
the  firing  being  done  at  the  water  level.  This  vertical 
component  of  course  measures  the  effective  velocity 
upon  which  deck-perforation  depends. 

At  45  degrees  elevation  the  vertical  component  is 
four  times  the  square  root  of  the  range  in  feet. 

At  60  degrees  elevation  the  vertical  comx)onent  is 
4.9  times  the  square  root  of  the  range  in  feet. 

At  75  degrees  elevation  the  vertical  component  is 
5.3  times  the  square  root  of  the  range  in  feet. 

Having  thus  formed  an  estimate  of  the  effective 
velocities  attainable  at  different  high  angles  and  at 
different  langes,  the  next  point  to  be  considered  is 
the  energy  necessary  to  accomplish  the  perforation  of 
the  deck. 

Actual  experiments  in  this  direction  with  vertical 
fire  are  few  in  number.  One  fact  noted  by  General 
Duane  at  the  attack  on  Fort  McAllister  throws  some 
light  on  the  subject.  A  10  inch  mortar-shell,  loaded 
with  sand  and  thrown  by  the  fort  at  a  range  of  about 


Vertical  Fire,  107 

1  800  yards,  just  penetrated  the  deck  of  one  of  our 
monitors,  which  was  plated  with  1.5  inches  of  iron. 
Assuming  that  the  shell  weighed  100  pounds,  and  that 
it  was  fired  at  45  degrees  elevation,  its  vertical  energy 
at  impact  was  about  1.9  foot-tons  per  inch  of  its 
circumference.  A  13-inch  shell  fired  under  like 
conditions  would  have  had  3.1  foot-tons,  and  would 
probably  have  endangered  the  vessel. 

Trials  in  England,  about  1871,  proved  that  a  13- 
inch  mortar-shell  at  4  200  yards  would  easily  pene- 
trate a  strong  deck  covered  with  1.5  inches  of 
wrought  iron  under  4.5  inches  of  wood  plank- 
ing (energy,  7.1  foot-tons  per  inch  of  circumference)  ; 
and  that  at  2  800  yards  it  would  penetrate  a  similar 
deck  covered  with  one  inch  of  wrought  iron  under  4.5 
inches  of  wood  planking  (energy,  4.7  foot -tons  per 
inch  of  circumference). 

In  the  absence  of  experimental  data  derived  from 
modern  vertical  fire,  recourse  must  be  had  to  the 
behavior  of  plating  when  tested  in  the  ordinary 
manner.  It  is  most  convenient  to  assume  wrought 
iron  as  the  basis  of  comparison,  because  its  resistance 
is  governed  by  more  definite  laws  than  that  of  any 
other  kind  of  armor  ;  and,  although  the  different 
formula3  representing  these  laws  are  not  entirely 
accordant,  they  are  fairly  so  for  small  penetrations. 
They  indicate  that  to  pierce  three  inches  of  wrought 
iron  requires  from  12.5  to  14.5  foot- tons  of  energy  per 
inch  of  the  shot's  circumference.  But  this  energy 
for  a  falling  projectile  is  : 

^^  WV ^       WY' 

2  240  X   2^  X  27tB  ~  906  000^ 

This  formula  shows,  since  Fis  a  function  of  the 
range  and  i:>ointing,  that  when  these  are  fixed  the 
only  way  to  increase  the  energy  at  impact  is  to  in- 
crease the  weight  relatively  to  the  radius.  But  this 
is  precisely  the  effect  of  rifiing;  and  herein  lies  the 


108 


Mortars  and  Submarine  Mines. 


first  advantage  resulting  from  its  use.  For  example, 
tlie  weight  of  a  12-inch  solid  shot  is  about  215  pounds  ; 
that  of  the  corresponding  elongated  projectile  is  about 
625  pounds.  Here,  therefore,  is  a  gain  of  nearly  200 
per  cent,  in  the  effective  force  of  impact — a  gain 
which,  by  reason  of  the  low  velocities  inherent  to  ver- 
tical fire,  is  of  great  importance.  It  may  even  be  in- 
creased at  short  ranges,  if  deemed  expedient ;  Krupp 
fires  a  projectile  weighing  759  pounds  from  a  28-cen- 
timetre (11-inch)  howitzer  at  58°  elevation. 

The  following  table  exhibits  the  destructive  ener- 
gies of  a  service  12-inch  rifled-mortar  projectile  fired 
at  different  angles  and  ranges.  It  illustrates  one  char- 
acteristic difference  between  horizontal  and  vertical 
fire  :  with  the  former  we  must  shorten  the  range  and 
lessen  the  elevation,  and  with  the  latter  we  must 
lengthen  the  range  and  increase  the  elevation,  to  in- 
crease the  destructive  effect. 

FALLING  ENERGY  OP  A12-INCn  625-LiB.  RIFLED  PROJECTILE. 


rOOT-TONS    PBK    INCH  OP 
CIRCUMFEatENCB. 

Bang©. 

§  . 

a  <v 

O  a> 

■ft 

Half-mile 

4.9 
S.7 

19.4 
29.1 

3a& 

48.6 

7.3 
14.6 

29.2 
43.7 
58.3 
72.9 

8.5 

One  mile ,.   ...   ....... 

17.1 

Two  miles 

34.1 

Three  miles 

51.2 

Four  miles 

68.2 

Five  miles 

As  already  stated,  it  requires  from  12.5   to  14  5 


Vertical  Fire.  109 

foot-tons  \)QV  inch  of  the  shot's  ckcumference  to  pen- 
etrate a  3-iiich  wroLiglit-iron  deck.  Hence  at  a  range 
of  one  mile  and  npward  the  fire  becomes  dangerous. 

The  second  merit  of  rifling  is  that  it  vastly  in- 
creases the  serviceable  range.  With  the  old  smooth- 
bore i3-iiich  mortar  the  full  charge  was  20  pounds, 
giving  a  range  of  4  200  yards,  of  which  not  more  than 
2  200  yards  were  effective  against  a  3-inch  deck. 
With  the  12-incli  rifled  mortar  these  figures  are  60 
pounds  and  9  000  yards,  of  which  7  200  yards  are 
effective.  Here,  therefore,  we  have  a  gain  of  325  per 
cent.  It  is  this  merit  that  makes  the  new  mortar  so 
useful  in  opposing  the  distant  bombardment  of  cit- 
ies by  modern  high-power  guns  on  sliij)board.  No 
admiral  would  exj)ose  his  ships  to  receive  such  blows 
on  their  decks  without  serious  concern  ;  and,  as  will 
soon  appear,  all  we  have  to  do  is  to  multiply  numbers 
and  provide  suitable  emphicements  to  obtain  an  occa- 
sional hit,  even  at  very  long  ranges. 

But  this  suggests  the  third  advantage  of  rifling — 
increased  precision  of  fire.  It  would  at  first  sight  ap- 
pear paradoxical  that  rifling  can  be  beneficial  with 
this  class  of  ordnance.  As  used  in  guns  it  tends  to 
keep  the  axis  of  the  projectile  always  pamllel  to  it- 
self. But  in  vertical  tire  this  would  make  the  shell 
fall  sideways,  which,  by  increasing  the  resistance  of 
the  air,  would  reduce  the  vertical  velocity,  and  by  op- 
posing an  unsymmetrical  shape  would  probably  cause 
an  irregular  flight.  But  experience,  the  only  sure 
guide  in  such  matters,  proves  these  anticipations  to 
be  groundless.  About  a  dozen  years  ago  experiments 
were  made  at  Shoeburyness  to  test  the  matter.  A 
large  target  was  inclined  at  such  an  angle  as  to  re- 
ceive the  trajectory  at  right  angles  to  its  plane ;  and 
it  was  perforated  by  a  round  hole,  not  by  one  shaped 
like  the  longitudinal  cross-section  of  the  projectile, 
as  would  have  been  the  case,  to  a  greater  or  less  ex- 


110  Mortars  and  Submarine  Mines. 

tent,  if  the  axis  had  remained  parallel  to  itself.  A 
little  flag  was  then  placed  in  the  open  fuse-hole,  and 
the  spectators  could  distinctly  perceive  that  the  axis 
remained  nearly  parallel  to  the  trajectory.  Knowing 
the  fact,  it  appears  probable  that  the  short  length  of 
the  bore  in  the  mortar  limits  the  velocity  of  rotation 
just  sufficiently  to  prevent  tumbling,  but  not  enough 
to  prevent  the  resistance  of  the  air  from  forcing  the 
projectile  to  turn  to  a  position  of  tangency.  How- 
ever this  may  be,  nothing  is  more  certain  than  that 
precision  of  tire  has  been  vastly  increased  by  rifling, 
as  will  appear  from  the  following  statement : 

During  the  civil  war  268  shots  were  fired  in  the 
Defences  of  Washington,  at  a  range  of  about  half  a 
mile,  to  determine  the  precision  of  fire  of  smooth- 
bore siege-mortars  in  the  hands  of  good  troops,  under 
fair  service  conditions.  It  was  found  that  with  the 
10-incli  mortar  the  average  distance  from  the  point 
of  impact  to  the  centre  of  the  target  was  40  yards, 
and  that  six-tenths  of  the  shells  fell  within  this 
radius.  With  tlie  8-inch  mortar  these  numbers  were 
.^0  yards  and  five-tenths  of  the  shells  respectively. 
With  the  24-pounder  Coehorn  mortar  (for  which  this 
range  is  too  great)  about  half  the  shells  fell  within  80 
yards  of  the  centre  of  the  target.  With  mortars,  as 
with  guns,  the  accuracy  of  fire  increases  with  the 
weight  and  density  of  the  projectile  ;  and  it  was  esti- 
mated that,  with  proper  care,  a  20-incli  smooth-bore 
mortar  would  throw  at  least  half  of  its  projectiles 
within  30  yards  of  the  centre  of  the  target  at  a  range 
of  1  000  yards  :  i.e.^  the  chances  should  be  even  that 
the  shell  will  fall  within  a  circle  of  which  the  area 
is  26  000  square  feet.  But  the  area  of  the  deck  of 
modern  war-ships  varies  between  about  4  000  and 
16  000  square  feet,  the  mean  (250  by  50  feet)  being 
about  12  500  square  feet.  Hence,  by  the  theory  of 
probabilities,  about  one  out  of  eight  20-inch  mortar- 


VerUcal  Fire,  111 

shells  (smooth-bore)  should  strike  her  at  1  000  yards 
from  the  battery  ;  at  2  000  yards  her  danger  would 
not  be  very  materially  reduced  ;  at  3  000  yards  the 
uncertainty  of  fire  would  so  much  increase  that  it  was 
estimated  that  not  more  than  one  shot  in  twenty-five 
would  take  effect.  Let  us  now  see  how  these  figures 
compare  with  the  results  to  be  expected  from  the 
modern  12-inch  rifled  mortar. 

At  the  Bucharest  experiments  of  1885-86  some 
valuable  data  were  obtained  as  to  the  precision  of  fire 
of  Krupp's  21-centimetre  siege-mortar.  The  range 
was  2  761  yards,  or  a  little  more  than  a  mile  and  a 
half.  The  charge  was  6.6  pounds  of  powder.  The 
projectiles  were  either  common  shell  weigliing  200 
I)ounds,  or  steel  shells  weighing  the  same  but  longer 
and  carrying  a  larger  bursting  charge  (24  pounds  in- 
stead of  10.5  pounds).  The  elevation  varied  between 
53°  and  56°.5. 

Two  mortars  were  used  :  70  shell  were  fired  at  the 
French  cupola,  and  94  at  the  German.  The  firing  oc- 
curred on  four  days,  that  at  the  French  cupola  com- 
ing first.  '  The  following  figures  show  separate  analy- 
se's,  an  evident  improvement  taking  place  during  the 
practice  : 

FRENCH  CUPOLA.   GERMAN  CUPOLA. 

Extreme  lateral  dispersion. .   273.4  yds.       76.5  yds. 
Extreme  dispersion  in  range.  393.7     ''       273.4     " 
Average  lateral  dispersion. .     16.2     "  9.7     " 

Average  dispersion  in  range.     44.2     '^         39.5     '' 

Out  of  these  164  shells,  70,  or  nearly  one-half,  fell 
within  a  rectangle  around  the  target  of  which  the  area 
was  about  17  000  square  feet  (20  x  80  metres).  Hence, 
the  area  of  the  deck  being  12  500  square  feet,  about 
one  projectile  out  of  five  or  six  fired  from  this  siege- 
mortar  at  a  range  of  1.5  miles  should  strike  a  modern 
war-ship  at  anchor.  The  exact  percentages,  comput- 
ed by  the  theory  of  probabilities,  are,  for  the  head-on 


112 


Mortars  and  Submarine  Mines, 


position  17^  and  30i^  per  cent.,  and  for  the  broad- 
side position  Wyi  and  14  per  cent,  respectively. 

With  mortars  large  enough  to  be  used  in  coast  de- 
fence experimental  data  are  not  so  full  as  could  be 
desired,  because  the  firing  has  not  been  made  under 
service  conditions.  The  chief  causes  of  bad  practice 
are  to  be  attributed :  (1)  to  mechanical  inaccuracies  in 
the  mortar  and  carriage  ;  (2)  to  want  of  uniformity  in 
the  ammunition  ;  (3)  to  errors  in  pointing ;  (4)  to  v^^ind 
and  other  unfavorable  conditions  ;  (5)  to  the  excite- 
ment of  action — although  to  this  last  little  weight 
should  be  accorded  in  mortar  practice  against  ship- 
ping, for  the  gunners  will  be  covered  so  perfectly 
against  any  return  that  the  veriest  coward  should  re- 
main cool. 

Precise  data  are  available  to  estimate  the  effect 
of  the  first-named  causes  of  inaccuracy  (mechanical 
defects  and  variable  ammunition)  in  Krupp's  tables 
of  firing  at  Meppen  : 

GERMAN    PRACTICE  WITH    28  CENTIMETRE   (11-INCH) 
HOWITZER. 


EXTREME 

1 

MEAN 

w. 
O 

1 

1 
1 

o 

i 

DISPERSION. 

DISPERSION. 

DATE. 

"3 
■'3 

"3 
'5 

i 

a 

w 

^ 

0) 

5 

2 

"i^ 

•Si 
5 

a 

To 

1 

a 

\ 

p 

lbs. 

lbs. 

yds. 

yds. 

yds. 

yds. 

yds. 

Mar.  30, 1887. 

5 

58 

13 

506 

1993 

36 

5 

11.9 

1.6 

July  9,  1886. 

5 

58 

19 

759 

2  158 

13 

13 

5.4 

3.3 

June  28, 1886 

8 

58 

33 

759 

4  019 

46 

15 

13.0 

4.7 

Mar.  14, 1879. 

10 

45 

42 

475 

8  513 

145 

24 

35.0 

4.5 

May  14, 1886. 

10 

45 

62 

475 

10  787 

130 

54 

36.2 

10.4 

Applying  the  calculus  of  probabilities  to  the  last 


Vertical  Fire. 


118 


two  records,  it  ax)pears  that  nearly  one  rifled  shell  out 
of  two  (65  per  cent,  in  the  head-on  position  and  15 
per  cent,  in  the  broadside  position)  should  strike 
the  deck  of  a  war-sliip  at  a  range  ol  4.8  miles  ;  and 
that  nearly  one  out  of  four  (81  per  cent,  in  the  head- 
on  position  and  14  per  cent,  in  the  broadside  position) 
should  take  effect  at  a  range  of  6.1  miles.  These  fig- 
ures, of  course,  give  an  exaggerated  idea  of  what  can 
be  expected  in  service,  because  the  other  causes  of 
inaccuracy  above  named  are  ignored.  What  numeri- 
cal coefficient  should  be  adopted  to  correct  for  these 
omissions  is  a  matter  of  individual  judgment. 

The  follown'ng  are  some  results  of  experimentill 
firing  with  an  11-inch  mortar  in  Russia  in  1885.  The 
princip;d  objects  were  the  testing  of  new  carriages, 
and  the  determination  of  the  maximum  charge 
under  the  condition  that  the  pressure  in  the  bore 
should  not  exceed  1  900  atmospheres.  These  charges 
were  fixed,  after  firing  400  rounds  with  fiiD  and  200 
with  reduced  charges,  at  46.9  pounds  with  a  cast- 
iron  1)1*0 jec tile  weighing  477  pounds,  and  at  45 
pounds  with  a  steel  projectile  weighing  559  pounds, 
the  grade  of  powder  being  "large  grain."  I  give 
the  table  showing  the  abstract  of  this  firing  in  full, 
because  it  illustrates  a  subject  concerning  which 
little  information,  is  accessible  : 

RUSSIAN  PRACTICE  WITH  11-lNCH  MORTAR. 


Weight 
of  pro- 
jectile. 

Weight 
charge. 

Initial 

veloc- 

ity. 

Pressure 
at  base 
of  bore. 

Bange 

at 
43°  30'. 

Probable  deviation. 

PROJECTILES. 

In  range. 

In    direc- 
tion. 

Cast  iron 

if 

Steel 

lbs. 

477 

477 
559 
559 
559 
559 

lbs. 
36.1 

46.9 

18.0 

27.1 

36.1 

45.1 

feet. 
758 

938 

482 

613 

735 

840 

atmos. 

1875 

1700 

yds. 
5  668 

7  412 

2  343 

3  597 

5  014 

6  431 

yds. 
24.0 

28.3 

17.6 

13.2 

19.8 

26.2 

yds. 
4.4 

6.5 

3.3 

«< 

2.2 

<< 

3.3 

<( 

4.4 

114  Mortars  and  Submarine  Mines. 

The  wonderful  precision  attained  in  this  practice 
proves  that  the  Krupp  firing  analyzed  above  was  not 
exceptional,  and  the  same  conclusion  is  warranted  by 
recent  records  of  firing  with  a  12- inch  mortar  at 
Sandy  Hook.  It  must,  therefore,  be  admitted  that 
modern  improvements  in  vertical  fire  have  kept  pace 
with  those  in  guns.  Indeed,  in  a  recent  analytical 
accuracy  table  it  appears  that  the  probability  of 
hitting,  with  the  projectiles  of  a  9-inch  mortar,  a  first- 
class  ship  of  war  lying  at  a  known  distance  diagon- 
ally to  the  plane  of  fire,  is  62  per  cent,  at  1.3  miles, 
51  per  cent,  at  2.6  miles,  and  32  per  cent,  at  4.0 
miles.  In  other  words,  it  is  about  half  that  of  Ijitting 
the  same  ship  with  a  rifled  gun  of  similar  calibre. 

These  results  of  the  practice  ground  are  not  with- 
out confirmation  in  actual  service.  On  May  10,  1877, 
a  Russian  shell  from  a  6-inch  rifled  mortar  (one  of 
four  in  position  near  Braila,  on  tlie  Danube)  "pene- 
trated the  deck  of  one  of  the  largest  Turkish  moni- 
tors, the  Luftl-Djelil^  and  exploded  in  the  powder- 
magazine.  She  blew  up  and  sank  instantly,  with  all 
her  crew  of  17  officers  and  200  men.  The  ship  was 
a  twin-screw,  iron- clad,  sea-going  monitor,  carrying 
four  150-pounder  Armstrong  guns." 

The  latest  development  in  mortar  practice  is  the 
reported  ability  to  throw  large  explosive  charges  of 
wet  gun-cotton.  It  is  stated  on  good  authority  that 
in  Germany  shells  containing  110  pounds  are  now 
fired  with  safety  from  a  28-centimetre  mortar.  If 
this  claim  be  verified  it  marks  an  important  advance  ; 
because  the  long  range  of  the  piece  will  enable  it  to 
throw  its  projectile  beyond  the  mined  zones,  and 
thus  avoid  the  objection  fatal  to  the  pneumatic  dyna- 
mite gun  that  it  assists  the  enemy  in  countermining. 

Carriages  and  Platforms. — No  better  evidence 
can  be  desired  of  the  low  estimate  which  until  within 
a  few  years  has  been  placed  upon  the  value  of  verti- 
cal fire  than  the  crude  mode  of  mounting  universally 


Vertical  Fire.  115 

adopted.  Every  practical  requirement  of  precision 
was  ignored  ;  hence,  in  my  judgment,  the  small  part 
which  mortars  formerly  played  in  projects  for  sea- 
coast  defence.  Since  their  value  has  been  better 
understood,  the  old  mortar  bed  with  its  eternal 
."heave,  heave,  heave,"  and  the  absurd  pointing-cord 
and  old  wooden  quadrant,  have  disappeared,  and 
artillerists  everywhej-e  are  giving  intelligent  consid- 
eration to  the  subject.  It  is  now  appreciated  that  so 
long  as  every  gunner  must  point  his  piece  indepen- 
dently, the  slow  flight  of  the  projectile  will  prevent 
him  from  recognizing  the  splash  of 'his  own  shell 
from  those  of  others ;  and  hence  the  more  numerous 
the  mortars  the  worse  will  be  the  firing. 

All  this  is  changed  in  the  new  system.  Mortars 
are  now  mounted  upon  chassis  like  guns,  and  the 
traverse-circle  is  graduated  so  that  they  can  be  accu- 
rately pointed  in  any  desired  vertical  plane.  The  ze- 
ros of  graduation  for  the  entire  group  to  be  served 
together  are  given  the  same  relative  position  with  re- 
spect to  the  meridian,  so  that  all  can  be  set  to  fire  in 
any  desired  set  of  parallel  planes.  By  this  system 
the  captain  regulates  every  shot  ;  and  if  the  mortars 
are  all  loaded  with  equal  charges,  set  at  equal  angles 
of  elevation,  and  adjusted  to  the  same  azimuth,  the 
shells  should  fall,  simultaneously  if  so  desired,  over  an 
area  not  greatly  larger  than  that  of  the  battery  itself. 

One  curious  fact,  which  has  a  bearing  upon  the 
practicability  of  firing  at  high  angles  on  board  ship, 
has  been  developed  quite  recently  in  experimenting 
with  new  mountings.  The  increase  of  weight  in  pro- 
jectile and  charge  has  so  largely  increased  the  shock 
on  the  carriage,  and  especially  on  the  platform,  that 
radical  changes  are  demanded. 

Thus  some  recent  experiments  in  Italy,  conducted 
by  the  Artillery  and  Engineer  Committee  with  a  28- 
centimetre  (11-inch)  howitzer  mounted  on  an  ordinary 
carriage,  with  a  charge  of  42  pounds  of  powder  and 


116  Mortars  and  Submarine  Mines, 

elevations  varying  from  30  to  60  degrees,  liave  proved 
that  the  shock  transmitted  to  the  platform  is  sur- 
prisingly difficult  to  resist.  A  platform  of  gianite,  24 
inches  thick,  laid  on  a  substratum  of  concrete  3  feet 
thick,  was  soon  cracked  and  thrown  out  of  level.  A 
second  platform,  covering  a  wider  area  of  concrete., 
and  with  larger  granite  blocks,  better  distributed, 
shared  the  same  fate.  The  third  trial  was  with  a  bed 
introducing  an  elastic  element.  Upon  the  concrete 
foundation  was  placed  a  layer  of  granite  16  inches 
thick ;  upon  this  was  laid  a  double  la^^er  of  oak 
beams,  each  10  inches  thick ;  upon  this  was  a  layer 
of  cast-iron  plates,  4  inclies  thick,  with  bevel  joints. 
Even  this  structure  developed  injurious  cracks  and 
settling,  although  still  serviceable  after  244  rounds. 
Finally,  for  the  fourth  trial,  a  platform  identical 
with  the  last  received  an  additional  top  layer  of  1.5 
inches  of  wrought-iron  plates.  This  structure  en- 
dured the  tiring  of  1  225  rounds  without  becoming 
unserviceable,  and  was  approved  for  adoption. 

But  the  use  of  wood  in  the  construction  of  per- 
manent works  has  always  been  regarded  with  dis- 
favor by  Engineers,  and  it  is  quite  natural  to  find,  as 
we  do,  that  efforts  are  making  to  introduce  the  ele- 
ment of  elasticity  in  some  other  way.  It  is  now 
sought  to  modify  the  carriage  in  su^li  a  manner  as  to 
reduce  the  shock  on  the  platform  ;  and  two  different 
patterns,  one  by  the  El:=wick  Ordnance  Company  and 
the  other  a  Russian  device  by  Lieutenant  E-askasoff, 
are  under  trial. 

The  Elsvvick  pattern  has  yielded  so  favorable  re- 
sults with  a  28  centimetre  (11-incli)  howitzer  at  Spez- 
zia  that  the  Italian  government  is  reported  to  have  de- 
cided to  order  a  large  number  for  service.  The  prin- 
ciple is  to  break  the  shock  of  recoil  by  interposing 
an  elastic  buffer.  The  chassis-rails  slope  to  the  rear 
at  an  angle  of  60  degrees  to  the  horizon.  The  top 
carriage,  resting  thereon,  is  supported  by  two  hydro- 


Vertical  Fire,  111 

pneumatic  buffers  fixed  below  and  in  prolongation  of 
the  cliassis-rails.  Each  cylinder  contains  two  cham- 
bers, connected  by  a  valve  which  can  be  regulated 
from  without.  One  chamber  is  filled  with  glycerine 
and  receives  the  recoil  ram  ;  tlie  other  contains  a 
supply  of  glycerine  and  air.  When  the  liowitzer  is 
fired  the  force  of  recoil  drives  the  rams  into  their 
chambers,  and,  displacing  the  columns  of  glycerine, 
forces  it  out  through  non-return  valves  into  tlie  outer 
chambers.  This  increases  the  normal  tension  of  the 
contained  air  and  glycerine  from  750  pounds  to  1  150 
pounds  to  the  incli.  To  raise  the  carriage  again  to 
the  firing  position  the  valve  is  opened  between  the 
cylinders,  and  the  equalization  of  pressure  tlius  ef- 
fected does  the  work.  The  whole  carriage,  mounted 
on  a  live  ring,  is  readily  turned  to  any  desired  azi- 
muth by  ordinary  training  gear.  Facilities  for  bring- 
ing the  axis  of  the  piece  to  a  horizontal  position  for 
convenience  in  loading  are  provided.  The  axis  of 
the  liowitzer  can  be  raised  or  lowered  15  degrees  from 
its  mean  elevation  of  60  degrees  in  firing,  thus  permit- 
ting of  elevations  ranging  from  45  to  75  degrees. 
The  carriage  supj)lied  to  the  Italian  government  is 
said  to  be  adapted  to  receive  an  li-inch  howitzer. 

The  new  Russian  carriage  is  similar  in  principle 
to  that  of  the  Elswick  Company,  but,  instead  of  the 
hydro-pneumatic  apparatus,  use  is  made  of  an  hy- 
draulic cylinder  and  a  system  of  steel-disc  springs. 
It  has  been  adapted  to  an  11-incli  mortar  made  on  the 
Krupp  system  and  12  calibres  long.  The  action  is 
entirely  automatic.  The  Committee  desire  to  com- 
bine low  as  well  as  high  angles  of  fire,  and  thus  are 
compelled  to  sacrifice  some  advantages  i^eculiar  to 
each.  Tlie  chassis-rails  slope  to  the  rear  at  an  angle 
of  only  35  degrees.  The  carriage  admits  of  an  ex- 
treme elevation  of  25  degrees  above  this  sloping 
plane,  or  of  60  degrees  as  referred  to  the  horizon. 
The  extreme  recoil  is  said  to  be  about  two  and  a  half 


118  Mortars  and  Submarine  Mines. 

feet.  Several  hundred  rounds  have  been  fired  with- 
out injury  to  a  pattern  of  platform  which  with  an 
ordinary  carriage  Avas  completely  shattered. 

It  is  quite  certain  that  modern  mortars  will  re- 
quire some  such  mounting  as  has  just  been  described, 
and  I  think  few  matters  connected  with  our  new  land 
armament  are  more  urgently  in  need  of  attention. 
The  Ordnance  Department  is  alive  to  the  necessity, 
and  it  is  to  be  hoped  that  Congress  will  soon  provide 
means  for  making  the  trials.  With  the  old  form  of 
carriage,  or  with  any  form  which  does  not  provide 
a  buffer,  our  Engineers  will  probably  be  forced  to 
introduce  wood  into  the  platforms.  But,  although 
experiments  have  been  made  in  this  direction  with 
creosoted  timber,  no  success  lias  been  had  in  prevent- 
ing decay  when  exposed  for  long  periods  ;  and  in  all 
probability  the  outbreak  of  war  would  find  such  plat- 
forms either  unlaid  or  unserviceable. 

Mortar  Batteries. — In  these  days,  when  Engi- 
neers are  compelled  to  deal  so  much  with  the  terrific 
energies  of  modern  horizontal  fire,  it  is  a  relief  to  find 
one  kind  of  effective  ordnance  which  can  be  mounted 
and  served  with  almost  absolute  safety  from  behind  a 
simple  earthen  parapet.  No  embrasures  with  their 
conflicting  conditions  are  to  be  devised,  and  an  ample 
thickness  of  earth  is  all  tliat  is  needful.  But  even 
this  statement  does  not  present  the  case  with  suf- 
ficient strength.  The  battery  may  be  entirely  con- 
cealed from  the  enemy — indeed,  would  usually  be  so 
concealed  by  natural  inequalities  of  the  ground,  or 
by  bushes  or  trees.  Even  a  view  of  the  ship  from 
the  battery  itself  is  unnecessary,  for  the  fire  will  al- 
waj^s  be  regulated  from  a  distant  point.  In  a  word, 
with  the  smoke  of  our  firing  as  the  only  target  for 
hostile  guns,  and  with  vertical  fire  (not  to  l)e  had  on 
shipboard)  only  to  be  dreaded,  it  is  easy  to  under- 
stand why  mortar-b^tteiies  are  simple  as  comx)ared 
with  all  others. 


Vertical  Fire,  119 

There  are,  however,  certain  matters  which  must 
not  be  ignored.  In  order  that  the  projectiles  shall 
fall  sufficiently  near  together  to  make  the  fire  effec- 
tive, it  is  essential  that  the  mortars  shall  be  massed, 
thus  constituting,  as  it  were,  a  single  piece.  Four 
mortars  may  be  placed  in  one  pit,  and  by  disposing 
four  of  these  pits  symmetrically  round  a  common 
centre  very  convenient  arrangements  for  serving  are 
secured.  A  compact  battery  containing  16  mortars 
logically  results  from  this  reasoning,  and  that  num- 
ber is  suitable  for  the  command  of  a  single  officer. 
Such  a  combination  constitutes,  in  effect,  a  single 
gigantic  musket  throwing  a  charge  of  buckshot  of 
which  each  pellet  weighs  a  quarter  of  a  ton  ! 

The  radius  of  the  circle  is  fixed  by  the  following 
considerations  :  On  the  one  hand,  the  lateral  and 
longitudinal  separation  of  the  pits  must  be  sufficient 
to  afford  space  between  tliem  ample  for  magazines, 
loading-rooms,  and  bomb-proof  cover  for  the  garrison. 
On  the  other  hand,  the  extreme  distance  between  pits 
must  be  limited  to  the  extreme  dispersion  of  the 
projectiles  of  a  single  mortar,  else  there  will  be  an 
area  of  safety  in  the  middle  of  the  field  of  fall. 
Lateral  dispersion  being  much  less  than  longitudinal 
dispersion,  this  condition  fixes  a  much  narrower  limit 
for  admissible  separation  of  the  pits  in  a  direction 
across  the  plane  of  fire  than  in  a  direction  parallel 
to  that  plane.  Indeed,  in  the  former  direction  the 
extreme  limit  can  hardly  be  avoided  ;  but  in  the 
latter  it  is  easy  to  secure  a  decided  overlapping  of 
the  rectangles. 

These  conditions  are  fulfilled  when  the  centres  of 
the  outer  mortars  in  each  pit  lie  on  a  circle  150  feet 
in  radius,  the  extreme  lateral  separation  being  140 
feet,  and  the  extreme  longitudinal  separation  being 
265  feet. 

The  arrangements  in  the  battery  are  simple.  One 
long  bomb-proof  extends  parallel  to  the  usual  plane 


120  Mortars  and  Submarine  Mines. 

of  fire,  with  debouches  into  each  pit  near  its  extrem- 
ities ;  the  magazines,  shell-rooms,  engine-rooms,  etc., 
are  X)laced  nnder  the  cross-embankment,  with  conjmu- 
nications  opening  into  the  middle  of  the  {;entral 
bomb-proof.  The  firing  will  all  be  done  by  electricity 
from  the  bomb-proof,  permanent  leading  wires  to  the 
mortars  being  laid  in  advance ;  all  the  work  of 
loading,  except  the  actual  insertion  of  the  shells  iti 
the  mortars,  will  also  be  done  under  cover ;  tlie 
cannoniers  will  be  exposed  only  when  loading  ;  and, 
lastly,  nothing  but  accident  can  bring  a  hostile  shell 
to  interrupt  the  steady  prosecution  of  the  firing. 

The  service  of  su(;h  a  battery  in  action  would  be 
something  like  the  following:  The  captain  woukl 
take  his  station  at  a  point  from  which  he  could  see 
the  enemy  engaged  at  some  work,  as,  for  example,  at 
countermining  in  our  mined  channel.  From  his  chart 
and  a  position-finder  he  would  determine  the 
elevation,  charge,  and  azimuth  for  a  trial  shot. 
Giving  his  orders  by  telephone,  he  would  watch  the 
splash  of  the  shell,  and,  estimating  the  deviation, 
would  give  orders  for  the  second  shot  accordingly. 
Having  succeeded  in  dropping  one  shell  in  close 
vicinity  to  the  enemy,  he  would  order  the  whole 
battery  to  adopt  the  same  elevation,  cliarge,  and 
azimuth,  and  to  fire  by  volleys  of  4  or  of  16  mor- 
tars, as  seemed  best.  After  that,  countermining, 
which  to  be  eifective  must  be  strictly  local,  could  be 
carried  on  only  under  great  disadvantages  ;  and  even 
in  an  attempted  distant  bombardment  the  only  safeiy 
for  the  fleet  would. lie  in  so  frequent  a  change  of 
position  as  to  destroy  any  precision  of  fire. 

To  fix  ideas  upon  the  probable  distribution  of  the 
projectiles  f lom  such  a  battery  containing  sixteen  12- 
inch  rifled  mortars,  I  have  discussed  the  foregoing 
German  and  Russian  data  with  ll-inch  mortars, 
which  afford  the  best  available  criterion  for  judging 
of  the  performance  of  the  latest  sea- coast  types.    The 


Vertical  Fire. 


121 


two  records  are  remarkably  accordant ;  and,  combin- 
ing those  at  4.8  and  4.2  miles  (8513  and  7412  yards)  as 
of  equal  weight,  they  give  the  following  results  when 
discussed  by  an  application  of  the  method  of  least 
squares. 

The  16  projectiles,  being  fired  under  identical 
conditions,  should  fall  in  relative  positions  corre- 
sponding to  those  occupied  by  the  mortars  themselves. 
But  the  units  of  each  sub-group  of  four,  being  situated 
at  the  angles  of  a  square  only  20  feet  on  the  edge, 
may  be  treated  as  a  compound  unit  in  the  computa- 
tion. The  mean  rectangle  containing  half  of  the  pro- 
jectiles of  a  single  mortar,  derived  from  the  combined 
records,  is  28  feet  wide  and  lt52  feet  long  in  the  plane 
of  fire.  Hence,  by  the  law  of  error,  the  following 
rectangles  result  : 

PERCENTAGE    RECTANGLES    IN     MORTAR    PRACTICE    AT 
4.5   MILES. 


Zone. 

Length- 

Width. 

Area. 

Receives 

Per  Cent. 

Feet. 

Feet. 

Sq.  Feet. 

Percent 

20 

62 

11 

653 

4 

40 

136 

22 

2  103 

16 

CO 

202 

35 

4  332 

36 

80 

308 

53 

9  287 

64 

100 

648 

112 

56  201 

* 

100 

An  over-lapping  tinted  diagram  is  next  prepared, 
showing  these  rectangles  in  their  proper  relative 
positions  ;  and  the  number  of  projectiles,  in  a 
volley  from  four  mortars,  falling  in  1  000  square, 
feet  of  each  tint  is  inscribed  thereon.  By  plac- 
ing a  tracing  of  the  Inflexible^  also  subdivided 
into  sections  of  1  000  square  feet,  in  any  desired 
position  on  this  diagram,  it  is  easy  to  estimate  her 
danger,  and  to  form  a  definite  idea  of  the  degree  of 


122 


Mortars  and  Submarine  Mines. 


precision  which  is  needful  in  the  officer's  determina- 
tion of  the  locus  of  the  ship  when  directing  the  firing. 
The  following  results  have  been  reached  by  this 
method.  To  define  the  different  positions  occupied  by 
the  middle  of  the  ship,  they  are  referred  to  a  rect- 
angular system  of  co-ordinate  axes,  parallel  to  the 
sides  of  the  rectangles  of  dispersion  and  central  to 
the  field  of  fall.  In  the  *' diagonal"  position  the 
keel  of  the  ship  makes  an  angle  of  45  degrees  Avith 
the  axis  of  X.  The  shots  per  hour  are  computed 
upon  the  supposition  that  six  volleys  are  fired, 
which  is  certainly  within  what  may  reasonably  be 
expected.  The  range,  it  will  be  remembered,  is  about 
four  and  a  half  miles. 

PROBABLE  PRACTICE  AT  THE  JKFLEXIBLJE  WITU  11-INCH 
MORTARS  AT  4.5  MILES. 


Position  op  the  Ship. 

(FEET) 

Hits  per 
Volley. 

Hits  per 
Hour. 

Effective  iier 
cent,  of 
Shots. 

Head  on. 

Central 

0.93 

5.6 

5.8 

(( 

X  =  60;Y  =  0 

3.24 

19.4 

20.3 

(( 

X  =  60;  Y  =  122 

2.84 

17.0 

17.8 

Broadside. 

Central 

2.21 

13.3 

13.8 

Diagonal. 

Central 

2.24 

13.5 

14  0 

X  :-  50  ;  Y  =  0 

1.87 

11.2 

11.7 

X  =  100  ;  Y  =  0 

1.40 

8.4 

8.8 

X  =  150  ;  Y  =  0 

0.69 

4.1 

4.3 

X  - .  0  ;  Y  =  100 

2.27 

13.6 

14.2 

X  -_  0  ;  Y  =  300 

1.69 

10.1 

10.5 

Xr^O     Y  =  300 

0.82 

4.9 

5  1 

X  =  0;  Y  =  400 

0.33 

2.0 

21 

X  =  0  ;  Y  =  500 

0.07 

0.4 

05 

Vertical  Fire.  123 

From  this  table  it  appears  that  the  fire  of  this  bat- 
tery, when  armed  with  11-iiich  mortars,  covers  a  space 
800  feet  long  and  300  feet  wide  so  effectively,  at  a 
range  of  four  and  a  half  miles,  that  the  Inflexible, 
within  its  limits,  would  probably  be  struck  from 
two  to  nineteen  times  per  liour. 

It  is,  of  course,  to  be  understood  that  computations 
of  this  character  afford  only  approximate  indications 
of  wliat  can  be  attained  in  service  ;  but  they  do  show 
that  with  this  form  of  battery  slight  errors  in  adjust- 
ing altitudes,  azimuths,  and  charges  will  have  far  less 
effect  than  when  the  same  number  of  mortars  are 
pointed  and  served  separately.  The  combination  of 
several  somewhat  erratic  projectiles  in  one  volley 
tends  to  eliminate  individual  lack  of  precision  and  to 
distribute  the  fall  over  the  dangerous  area  even  more 
uniformly  than  theory  requires.  The  risk  in  occupy- 
ing the  field  of  fire  is  enormously  increased  ;  and  even 
one  such  16-mortar  battery,  skilfully  served,  should 
go  far  to  deter  a  ship  from  anchoring  anywhere 
within  a  range  of  from  one  to  five  miles  with  a  view 
to  the  bombardment  of  a  distant  city. 

Economy  of  Mortars.— The  cost  of  mortars 
themselves  is  small  compared  with  that  of  guns,  for 
they  are  not  so  much  exposed  to  excessive  powder- 
pressures,  and  may  perhaps  be  made  even  of  cast 
iron  if  any  trustworthy  mode  of  loading  at  the  breech 
Ccin  be  adapted  to  that  material.  The  additional 
weight  needful  with  cast  iron  is  perhaps  no  disad- 
vantage in  view  of  the  difficulty  of  controlling  recoil ; 
but  experience  at  Sandy  Hook  indicates  that  breech- 
loading  is  essential  to  give  the  regular  and  uniform 
velocity  of  rotation  upon  which  precision  of  fire  de- 
pends. With  muzzle-loading  in  so  short  a  bore,  the 
expanding  sabot  acts  irregularly,  and  the  shells  are 
liable  to  tumble  or  to  take  up  a  wabbling  flight  incon- 
sistent with  uniformity  of  range. 


324  Mortars  and  Submarine  Mines. 

The  cost  of  a  mortar-battery  is  trifling  as  com- 
pared with  that  for  guns.  Including  masonry  maga- 
zines for  a  large  supply  of  ammunition,  bomb  proofs 
of  ample  size  for  all  the  needs  of  tbe  garrison,  and  en- 
gine and  boiler-rooms  for  supj^ilying  power  for  serv- 
ing the  pieces,  the  cost  would  range  from  $2  000  to 
$6  000  per  mortar,  according  to  the  local  requirements 
of  the  site.  I  constructed  at  Willets  Point  in  1872 
a  16-mortar  battery  embodying  the  above  principles, 
at  a  total  cost  of  $25  000. 

But,  it  may  be  asked,  why  do  not  mortar-batteries, 
with  all  these  merits,  solve  the  problem  of  a  modern 
coast  armament,  and  thus  render  unnecessary  the 
heavy  expense  of  high-power  steel  guns  and  armored 
defences  in  which  to  mount  them  %  Two  defects  in- 
herent in  vertical  fire  furnish  the  answer.  It  can 
only  be  used  with  effect  upon  vessels  under  way  by 
the  aid  of  a  tlieoretically  peifect  system  of  position- 
finding  ;  and  from  lack  of  energy  in  the  projectiles  it 
is  little  to  be  dreaded  at  short  ranges.  If  the  enemy 
can  approach  much  within  a  mile,  no  destructive 
blow  will  be  struck  by  a  descending  projectile  flred 
pven  at  75°  elevation.  The  best  held  for  horizontal 
lire  is  thus  the  worst  for  mortars  ;  they  are  allies  but 
not  substitutes. 

SUBMARTl^E   MI:NES. 

General  Conditions.  —  The  following  are  the 
general  conditions  which  military  engineers  consider 
should  be  fulfllled  by  this  system  of  channel  ob- 
structions : 

First.  The  mines  must  be  so  arranged  as  to  admit 
of  the  safe  passage  of  our  own  vessels,  while  they 
can  instantly  be  rendered  dangerous  to  the  enemy. 
This  condition  can  only  be  fulfilled  by  employing 
electricity  as  the  igniting  agent.  When  there  are 
several  parallel  channels,  it  may  be  admissible   to 


Submarine  Mines.  125 

close  some  of  them  by  self-acting  mines  ;  but  such 
instances  are  exceptional,  not  the  rule. 

Second.  Mines  which  can  be  exploded  only  by 
judgment,  at  tlie  will  of  an  operator  on  shore, 
have  a  very  limited  api^lication.  In  the  night,  or 
a  fog,  or  the  smoke  of  a  bombardment,  or  when 
several  vessels  are  a]3proaohing  abreast,  or  when 
the  water  is  deep,  or  when  the  channel  is  wide, 
the  chances  of  failure  are  very  great.  Indeed, 
the  destructive  range  of  practicable  charges  is  so 
limited  that,  if  the  ship  be  constructed  with  double 
cellular  bottom  and  water-proof  compartments, 
judgment-firing  has  become  nearly  obsolete  for 
any  but  very  narrow  channels.  In  general,  there- 
fore, the  system  must  be  automatic,  the  explosion 
occurring  in  consequence  of  the  touch  of  the  ene- 
my; but  it  should  also  admit  of  j^idgment-liring 
by  groups  when  desired. 

To  meet  the  ccmtingency  of  interference  by  our 
own  vessels,  or  the  use  of  defensive  outriggers  by 
the  enemy,  provision  must  be  made  to  delay  the  ex- 
plosion after  contact,  if  desired,  until  the  order  to 
lire  can  be  given  by  "the  officer  directing  the  defence. 
Since  the  apparatus  must  be  operated  in  a  casemate, 
from  which  no  view  of  the  channel  can  be  had,  this 
condition  implies  not  only  an  arrangement  of  the  ap- 
paratus by  which  a  contact  may  report  itself  without 
firing  the  mines,  but  also  a  telegraphic  communica- 
tion with  the  ramparts.  As  a  vessel  moving  at  a 
high  rate  of  speed  will  remain  only  a  few  seconds 
within  dangerous  range  of  a  mine,  a  perfect  code  sys- 
tem is  essential. 

Third,  The  mines  should  be  so  disposed  as  to 
cover  a  large  area  of  the  channel.  It  is  not  enough 
to  oppose  a  narrow  belt  of  danger.  The  waters 
well  to  the  front  of  the  forts,  under  their  close  lire, 
and  far  to  the  rear,  must  be  dreaded  by  the  enemy. 


126    .         Mortars  and  Submarine  Mines. 

Fourth.  Since  the  mines  may  remain  in  position 
for  long  periods,  the  system  must  provide  electrical 
tests,  by  which  the  condition  of  every  part  may 
often  be  verified  in  detail;  and  it  must  also  be  ar- 
ranged to  admit  of  rex-)airs  in  case  of  need. 

Fifth.  All  of  the  mechanical  arrangements  of 
the  mine  must  be  simple,  enduring,  and  strong 
enough  to  resist  shocks  from  friendly  vessels  and 
from  the  explosion  of  neighboring  mines  ;  and  special 
precautions  against  twisting  and  undue  dex)ression  by 
currents  must  be  taken  for  all  floating  parts. 

Sixth.  Every  practicable  auxiliary  expedient 
should  be  adopted.  Movable  torj^edoes  controlled 
from  the  shore,  and  the  electric  light,  are  obvious 
aids.  In  addition,  the  operating  apparatus  should 
be  arranged  to  provide  for  the  automatic  firing  of 
flanking  guns  in  case  of  any  disturbance  of  the  sys- 
tem by  the  enemy  under  cover  of  night  or  fog.  The 
electric  cable  should  have  sufficient  weight  to  sink 
into  the  mud  in  favorable  localities,  thus  increasing 
the  difficulty  of  boat-grappling  ;  strong  hemp  cables, 
weighted  at  short  intervals,  should  be  anchored  in 
the  mine  field  with  the  same  object  in  view  ;  and, 
lastly,  dummy  mines  and  false  buoys  should  not  be 
neglected. 

As  to  the  disposition  of  the  mines  in  the  channel 
engineers  are  not  entirely  agreed.  Some  limit  them 
to  two  or  three  well-defined  lines  which  cannot  be 
traversed  because  the  least  distance  between  contigu- 
ous mines  is  less  than  the  width  of  a  ship  of  war.  One 
fatal  objection  to  this  mode  of  planting  is,  in  my  judg- 
ment, that,  with  the  practical  difficulties  to  be  en- 
countered in  most  places,  it  is  impossible  to  plant 
mines  so  near  together  without  bringing  some  of  them 
accidentally,  in  so  close  proximity  that  one  explosion 
will  endanger  the  neighboring  mines.  A  still  stronger 
objection  to  the  plan  is  that  it  greatly  favors  the 


Submarine  Mines.  127 

kind  of  attack  we  have  most  to  dread,  that  by  counter- 
mines. Such  minute  refinements  are  out  of  place 
under  water.  If  it  is  known  or  believed  that  the  chan- 
nel for  three  or  four  miles  is  thickly  studded  with 
effective  mines,  the  enemy  will  never  attempt  to  run 
past  until  he  has  found  some  way  of  opening  a 
reasonably  safe  passage.  Nothing  is  so  certain  as 
chance  in  such  cases  ;  and  the  knowledge  that  the 
individual  mines  are  none  of  them  nearer  than  even  a 
couple  of  hundred  feet  of  each  other  will  not  induce 
a  wise  man  to  try  to  run  the  gauntlet  unless  he  can 
see  them.  In  other  words,  I  believe  that  it  is  the  total 
number  of  the  mines  rather  than  great  exactness  of 
location  which  will  best  bar  the  passage.  But,  on  the 
other  hand,  it  would  be  almost  impossible  to  thorough- 
ly defend  a  channel  without  having  some  regular  sys- 
tem of  working.  The  cables  would  become  hopelessly 
entangled,  so  that  no  repairs  of  tiie  system  would  be 
possible,  if  each  mine  were  planted  independently  of 
the  others.  Hence  the  use  of  the  multiple  (seven- 
cored)  cables  leading  to  separate  groups  becomes  a 
necessity ;  and  these  groups  can  be  planted  more 
readily  by  assigning  definite  positions  to  the  mines. 
Moreover,  by  placing  three  mines  on  each  separate 
cable,  each  of  them  will  explode  singly  if  struck  ; 
while  all  three  will  be  exploded  simultaneously  when 
fired  at  the  will  of  the  operator  on  shore.  The 
efficiency  of  the  whole  system  will  be  increased  by 
this  mode  of  planting,  and  the  use  of  the  enormous 
chai'ges  favored  in  France  and  in  some  other  countries 
will  be  avoided. 

For  these  and  other  reasons  it  appears  desirable  to 
cut  the  field  by  continuous  lines,  with  ample  inter- 
vals between  mines  to  prevent  them  from  becoming 
mutually  destructive  when  fired  ;  and  to  fill  the  gaps 
between  lines  by  single-cable  mines  admitting  only  of 
automatic  action.    Upon  this  system  it  is  possible  to 


128  Mortars  and  Submarine  Mines. 

thorougUy  obstruct  a  large  area  of  cliannel  without 
increasing  to  an  extravagant  extent  the  total  number 
of  individual  mines. 

There  are  two  other  mine  systems  which  require 
special  arrangements.  The  object  of  one  is  to  obstruct 
a  restricted  area  available  for  occupation  in  conduct- 
ing a  distant  bombardment ;  this  is  specially  easy  if 
the  water  be  so  shalloAvas  to  permit  the  use  of  ground- 
mines.  A  few  large  and  carefully  located  charges, 
arranged  preferably  for  judgment-tiring  (so  that  their 
discovery  by  sweeping  shall  be  made  as  difficult  as 
possible),  will  reinforce  mortar-firing  in  a  very  ef- 
fective manner.  Such  mines,  technically  called  "de- 
tached groups-,"  will  certainly  be  used  to  cover  an- 
chorages like  that  near  Coney  Island,  whence  a  ves- 
sel, without  crossing  the  bar,  might  annoy  Brooklyn. 
The  system  permits  the  use  of  cable  too  much  de- 
teriorated for  automatic  firing,  and  may  have  an  ex- 
tended application  under  certain  contingencies. 

The  other  special  system  is  emi)loyed  when  we  can 
afford  to  sacrifice  one  or  more  channels  because  we 
have  the  use  of  a  better  one  defended  by  electrical 
mines.  Such  an  obstruction  would  be  made  by  the 
use  of  self-acting  mines,  dangerous  alike  to  all  comers. 
The  only  remark  I  have  to  make  in  respect  to  this  class 
is  that  no  pattern  which  fails  to  fulfil  three  conditions 
should  be  received  with  favor.  These  conditions  are, 
iV)  that  no  safety  arrangement  which  requires  the  act 
of  the  planting  party  to  remove  is  admissible  ;  (2)  that 
some  arrangement  to  cause  the  immediate  explosion 
of  the  charge  if  the  mine  goes  adrift  is  essential ;  and 
(3)  that  every  possible  means  should  be  taken  to  make 
the  removal  difficult.  There  appears  to  be  a  differ- 
ence of  opinion  among  engineers  as  to  this  last  point ; 
but  I  think  it  arises  from  overlooking  the  fact  that 
it  is  impossible  to  easily  remove  ourselves  what  an 
enemy  informed  as  to  the    mechanism   cannot  also 


Submarine  Mines.  129 

readil}^  clear  away.  No  compromise  in  such  a  case 
is  possible.  If  we  want  efficiency  we  must  pay  tlie 
price  by  incurring  difficulty  in  oijening  the  channel 
when  the  need  for  tlie  obstructions  has  passed. 

This  same  class  of  self-acting  mines  may  some- 
times find  useful  employment  in  repairing  injuries 
done  to  a  regular  system  of  electrical  mines  by  coun- 
termining. To  be  of  much  use  the  passage  opened  by 
the  enemy  must  be  well  marked  and  buoyed.  A  few 
self-acting  mines  dropped  in  it  by  night  would  prove 
extremely  dangerous  ;  and  such  mines  are  very  easily 
handled  and  rapidly  planted.  All  that  is  necessary 
to  render  the  expedient  easy  of  application  is  to 
adapt  the  special  parts  of  the  self-acting  mechanism 
to  the  ordinary  electrical  mine,  so  that  when  desired 
it  may  be  planted  to  act  in  either  capacity. 

To  operate  electrical  submarine  mines  success- 
fully, large  voltaic  batteries  and  delicate  apparatus 
of  various  kinds  are  indispensable.  To  expose  this 
material  to  boat  attacks,  or  even  to  distant  bombard- 
ment, would  be  inadmissible,  for  even  a  slight  in- 
jury here  might  open  the  channel  to  the  enemy. 
The  operating  ai:)paratus  is  the  most  vulnerable  pait 
of  the  sj^stem  ;  hence  the  accepted  principle  that 
mines  must  be  served  from  strong  land  fortifications. 
A  sunken  gallery  leads  from  the  water  edge  at  lowest 
tide,  under  the  foundations  of  the  fort,  to  a  vertical 
shaft  oiDening  into  a  bomb-proof  casemate  which 
contains  the  apparatus.  This  apparatus  is  connected 
with  the  ramparts  by  telegraph,  so  that  the  engineer 
is  fully  informed  as  to  what  is  electrically  reported 
by  the  ndnes,  and  at  the  same  time  is  able  to  see 
what  the  enemy  is  doing  and  to  take  measures  ac- 
cordingly. 

Attacks  by  Daylig'ht. — Where  the  defence  is 
believed  to  be  weak,  shii^s,  by  the  use  of  outrigger 
frames  or  wire-rope  crinoline,  may  try  to  explode  at 


130  Mortars  and  Submarine  Mines. 

a  safe  distance  such  mines  as  may  chance  to  be  en- 
countered. But  with  electrical  mines  the  engineer 
will  simply  delay  the  explosion  until  the  torpedo  has 
passed  under  her  bottom  ;  or,  if  such  devices  should 
ever  be  made  really  practicable,  he  will  plant  his  cir- 
cuit-closer buoys  a  little  in  rear  of  his  mines,  and 
thus  cause  the  explosion  to  occur  precisely  where  he 
wants  it.  Finally,  the  crinoline  being  certainly 
swept  away  by  the  first  explosion,  the  ship  will  be 
left,  encumbered  by  the  wreck,  among  other  mines 
equally  dangerous. 

Should  divers  be  sent  forward  to  destroj^  the  sys- 
tem, so  soon  as  their  work  is  revealed  by  the  electri- 
cal indications  a  mine  fired  in  the  vicinity  will  at 
once  put  an  end  to  their  labors. 

If  old  hulks,  steered  by  electricity,  be  sent  for- 
ward to  explode  the  mines  in  the  channel,  or  if  rafts 
provided  with  grapnels  be  allowed  to  drift  in  with 
the  tide,  the  engineer  will  switch  off  his  batteries  ; 
and,  although  injury  may  result,  a  terrible  uncertain- 
ty will  be  left  to  the  enemy  as  to  how  many  perfect 
mines  may  still  be  waiting  to  receive  him. 

Remembering  that  a  cleared  and  buoyed  passage 
is  a  sine  qua  non  for  the  fleet,  and  that  by  daylight 
the  guns  of  the  fort  will  sweep  the  mined  zone  with  a 
murderous  fire,  the  uncertainty  of  any  unsystematic 
attack  is  apparent.  The  only  successful  method  of 
attacking  land  mines  has  been  shown,  by  the  experi- 
ence of  centuries,  to  be  by  countermines,  and  I  be- 
lieve that  future  wars  will  teach  the  same  lesson  for 
sea  mines. 

Steam-launches,  controlled  by  electricity  or  other- 
wise, or  small,  heavily  armored  vessels  made  for  the 
purpose,  will  move  up  to  the  supposed  outer  limit 
of  danger  ;  will  plant  from  one  to  four  500-pound 
counteruiines  ;  will  back  off,  and  by  exploding  them 
by  electricity  will  destroy  any  mines  in  the  immedi- 


I 


Submarine  Mines,  131 

ate  vicinity.  The  vessel  will  then  steam  forward  into 
the  vortices  and  plant  one  or  more  buoys.  By  re 
peating  this  operation  it  is  clear  that  n  safe  channel 
maybe  opened  and  plainly  marked ;  and  that,  finally, 
the  fleet  will  be  free  to  move  rapidly  tli rough  it  past 
the  guns. 

These  countermining  operations,  however,  will  be 
neither  expeditious  nor  safe.  The  vessel  will  neces 
sarily  indicate  her  successive  positions  of  rest,  and 
the  mortars  and  guns  will  prepare  volleys  for  her 
reception  at  i)oiiits  where  her  exact  locus  is  known. 
Movable  torpedoes  under  control  from  the  shore  will 
assail  her  below  the  armor  belt,  however  massive  that 
may  be.  By  night  new  mines  will  be  dropped  in  her 
buoyed  channel.  In  fine,  the  delays,  disasters,  and 
murderous  struggles  familiar  in  land-mining  will  in 
future  wars  find  their  counterparts  on  the  sea. 

Attacks  by  Night  or  in  Fog^s.— Under  such 
conditions  the  firing  of  the  guns  and  the  operating 
of  the  mines  cannot  be  so  intelligently  directed  by 
the  defence  ;  but,  on  the  other  hand,  the  enemy  can 
derive  little  information  as  to  the  details  of  the  dam- 
age inflicted,  unless  he  sends  boats  forward  to  work 
systematic  mischief  and  to  drop  buoys  accordingly. 
How  to  defend  the  mines  against  boat  attacks  con- 
ducted when  shrouded  from  view  becomes,  therefore, 
an  important  engineering  problem.  The  best  of  all 
assistance  can  be  rendered  by  a  flotilla  of  naval  j)ick- 
et  and  torpedo-boats  ;  but  when  they  cannot  be  had, 
four  useful  auxiliaries  may  be  employed — fouling- 
lines,  automatic  action  of  the  guns,  the  electric  light, 
and,  last  but  not  least,  movable  torpedoes  under  con- 
trol from  the  shore.  I  shall  say  a  few  words  as  to 
how  engineers  propose  to  make  use  of  each  of  these 
auxiliaries. 

Nets  to  foul  propellers  are  too  well  known  for 
discussion.    As  a  defence  against  attempts  to  grapple 


132  Mortal's  and  Submarine  Mines. 

the  cables,  whether  by  drifting  rafts,  or  by  the  some- 
what fanciful  scheme  of  mortar-boats  throwing  grap- 
nels, or  by  ordinary  steam-launches  or  small  boats, 
a  few  hawsers  anchored  in  front  of  and  among  the 
mines  will  certainly  be  found  useful.  They  should 
be  attached  to  the  heavy  anchors  or  blocks  of  stone 
used  to  hold  them  in  position,  by  short  lashings,  to 
prevent  them  from  being  drawn  under  the  mud. 
Multiple  cables  for  mines  soon  bury  themselves  by 
their  own  weight  in  the  soft  bottom  of  many  of  our 
harbors  ;  and,  as  a  harmless  hawser  can  only  be  de- 
tected by  raising  it,  the  enemy  must  either  lose  time 
in  so  doing,  or,  if  use  be  made  of  explosive  grapnels, 
he  will  be  led  to  over-estimate  the  damage  he  is  in- 
flicting. 

Main  lines  of  mines  should  be  so  arranged  as  to 
be  swept  throughout  their  length  by  the  fire  of 
flanking  guns.  These  guns,  charged  with  canister, 
grape,  or  shrapnel,  according  to  the  range,  should  be 
trained  by  daylight  to  sweep  their  respective  fields. 
Cables  extended  to  the  mining  casemate  place  these 
guns,  in  groups,  in  connection  with  the  electrical 
system,  and  any  injuries  to  mines  or  cables  will  at 
once  draw  the  fire  of  the  guns  ]3ointed  to  annoy  the 
boat  which  has  done  the  mischief.  The  artillery  offi- 
cers are  thus  informed  that  parties  are  grappling  and 
that  their  position  lies  in  a  certain  direction.  Know- 
ing the  latter,  they  will  keep  up  such  a  fire  as  will 
stop  or,  at  any  rate,  greatly  harass  the  boats. 

As  to  the  utility  of  the  electric  light  in  channel 
defence,  I  think  a  better  idea  can  be  formed  after  it 
has  been  more  fully  tried  in  war.  Before  firing  be- 
gins it  will  doubtless  be  very  useful,  but  so  soon  as 
the  air  becomes  obscured  by  smoke  from  the  guns,  or 
from  smoke-balls  burned  for  the  purpose,  experience 
leads  me  to  doubt  its  value.  It  will  be  most  useful 
in  clear,   dark  nights  ;  in  bright  moonlight  nights, 


Sabmarine  Mines.  133 

and  especially  in  fogs,  I  think  little  dependence 
will  be  placed  on  its  assistance  by  engineers. 

Tlie  usual  dispositions  of  the  apparatus  in  a  fort- 
ress are  to  place  the  engines  and  dynamo  in  a  bomb- 
proof casemate,  and  to  throw  the  beam  from  a  station 
near  the  water-level,  either  directly  or  by  reflectors, 
according  to  circumstances.  Stations  sliould  be  du- 
plicated and  be  placed  near  the  flanl<LS  of  the  position, 
to  avoid  smoke  driven  by  the  wind. 

In  the  absence  of  an  effective  tire  of  artillery,  and 
particularly  when  special  vessels  shall  have  been 
constructed  for  countermining,  movable  torpedoes 
controlled  from  the  sliore  can  be  made  to  play  an 
important  part.  Unless  the  currents  are  strong  there 
is  no  urgent  need  of  very  high  speed,  say  above  10 
miles  per  hour.  The  most  valuable  jjoints,  from 
an  engineer  standpoint,  are  :  (1)  Invulnerability  to 
fire,  whether  of  machine  guns,  of  rapid-firing  guns, 
or  of  cannon  throwing  grape  and  canister.  (2)  Ca- 
pacity to  carry  three  or  four  hundred  pounds  of  the 
explosive.  (3)  A  range  of  at  least  two  miles.  (4) 
The  power  of  diving  under  any  simple  boom  pro- 
tection, such  as  a  sbip  could  easily  improvise  from 
lier  spare  stores.  The  ordinary  service  conditions, 
such  as  being  under  perfect  control,  presenting  a 
small  target,  etc.,  etc.,  of  course  are  essential.  All 
these  conditions  can  be  fultilled  in  practice,  and  I 
entertain  no  doubt  that  such  boats  will  form  an  im- 
portant but  subordinate  element  in  every  perfect  sys- 
tem of  coast  defence. 

Much  has  been  said  of  late  as  to  the  probability 
of  torpedoes  of  this  class  being  superseded  by  large 
charges  of  dynamite  or  other  high  explosives,  thrown 
by  pneumatic  mortars  (usually  called  guns),  and  pro- 
vided with  fuses  which  cause  explosion  either  at  im- 
pact or  when  submerged.  In  advance  of  official  re- 
ports it  would  be  premature  to  foim  any  decided 

f/T^  Of    THt  ^ 

(UNIVERSITY  j 


134  Mortars  and  Submarine  Mines. 

opinion  on  the  subject ;  but  it  is  certain  that  one 
fatal  objection  would  lie  to  this  proposed  application 
— we  could  liardly  fail  to  damage  our  mines,  and  thus 
perform  for  the  enemy  work  which  it  is  the  part  of 
wisdom  to  force  him  to  undertake  himself.  The  con- 
trollable torpedo  causes  one  explosion  under  the  bot- 
tom of  the  counteiminer,  and  tliis  is  far  preferable 
to  many  explosions  well  distributed  by  ourselves 
among  the  mines  upon  which  our  successful  defence 
depends. 

Attempted  Passage  by  Force, — After  the  ene- 
my imagines  that  he  has  opened  a  clear  channel 
through  the  mined  field  he  will  attempt  to  force  a 
passage.  The  following  preparations  will  be  natu- 
rally made  :  The  position  of  tlie  commanding  officer, 
of  the  chief  of  artillery,  and  of  the  engineer  in 
charge  of  the  mines  will  be  at  some  selected  place 
where  smoke  from  the  guns  will  not  be  likely  to  an- 
noy them  ;  where  the  instruments,  so  far  as  possible, 
can  be  kept  under  cover  ;  and  where  a  good  view  can 
be  had  of  the  mined  zone.  Two  electric  cables  ter- 
minate at  this  station.  One  extends  to  the  mining 
casemate  for  telegraphic  communication  ;  the  second 
leads  to  the  other  extremity  of  a  base  line,  for 
triangulatitms  to  fix  exactly  the  position  of  the  enemy 
— unless,  indeed,  some  superior  method  of  position- 
finding  be  used. 

The  map  of  the  channel  being  always  at  hand, 
with  the  locus  and  condition  of  the  mines  and  the 
successive  positions  of  the  enemy  as  he  approaches 
laid  down  upon  it,  the  commanding  ofiicer  will  always 
understand  the  state  of  affairs  ;  and  the  engineer  can 
direct  the  service  of  his  mines,  and  the  artillery  offi- 
cer that  of  his  guns,  under  every  possible  advan- 
tage. 


Fifth  Lecture, 


SEA-COAST  FORTRESSES. 

Historical  resume  of  Coast  Defence  in  America — Resistance  to  projec- 
tiles; armor;  masonry;  earth — Approximate  formulae — Fortifica- 
tion of  the  site  selected — Naval  co-operation. 

Having,  in  the "  previous  lectures  of  this  course, 
passed  in  review  the  general  principles  of  the  art  of 
war  applicable  to  sea-coast  defence,  the  probable 
nature  of  the  naval  attacks  which  will  be  brought 
against  the  works,  the  financial  aspects  of  the  ques- 
tion, the  selection  of  suitable  positions  for  the  bat- 
teries, mines,  etc.,  and  the  character  of  the  several 
elements  composing  them,  it  remains  to  consider  how 
the  latter  are  to  be  combined  at  any  site  to  constitute 
a  sea-coast  fortress. 

If  our  coasts  were  entirely  devoid  of  defensive 
works  the  problem  would  be  different  from  that  now 
presented.  To  take  a  broad  view  of  the  subject  it  is 
needful  to  appreciate  what  the  existing  works  were 
designed  to  accomplish,  to  understand  their  construc- 
tion in  some  detail,  and  to  consider  what  use  can  be 
made  of  them  under  the  changed  conditions  of  the 
problem  now  presented.  I  shall,  therefore,  first  ask 
your  attention  to  a  brief  outline  of  the  development 
of  sea- coast  fortification  in  this  country. 

HISTORICAL       KESUME      OF      COAST     DEFENCE      IN 
AMERICA. 

Previous  to  the  Revolution  our  seaport  towns 
were  villages,  and  naval  establishments  and  military 


136  Sea-coast  Fortresses. 

depots  were  unknown.  The  harbors  of  Boston,  New 
York,  Philadelphia,  Charleston,  etc.,  had  been  pro- 
tected by  a  few  insignificant  earthen  forts  ;  but  at  the 
outbreak  of  war  the  sparse  population  and  long 
coast  line  enabled  the  mother- country  to  use  the 
ocean  for  her  base,  and  to  operate  where  she  wished 
until  the  French  appeared  on  the  scene.  A  small 
work  of  sand  and  palmetto-logs  in  Charleston  harbor, 
however,  under  the  command  of  Colonel  Moultrie,  de- 
cisively repuls^ed  the  attack  of  a  British  fleet  of  two 
frigates  and  six  sloops  of  war  (80  guns  against  270) 
in  1776,  and  thus  taught  our  people  the  value  of  for- 
tifications. The  battle  lasted  ui3ward  of  ten  hours, 
and  its  result  gave  a  local  respite  from  the  calamities 
of  war  for  two  and  a  half  years. 

Shortly  after  peace  had  been  declared  Washing- 
ton urged  the  necessity  of  defending  the  coast,  and 
the  French  troubles  drew  popular  attention  to  the 
subject.  Fort  Columbus,  Castle  Williams,  and  Cas- 
tle Clinton  (now  known  as  Castle  Garden)  were  built 
in  New  York  harbor  ;  and  in  nearly  all  of  our  chief 
ports  batteries  made  their  appearance,  but  they  were 
of  so  defective  design,  and  so  weak  and  perishable 
in  material,  as  to  have  no  permanent  value.  This 
(known  among  engineers  as  our  second  system  of  de- 
fence) did,  however,  some  service  in  the  war  of  1812. 
New  York  and  Boston  were  blockaded,  not  occu- 
pied ;  but  the  shores  of  Long  Island  Sound  and 
Chesapeake  Bay  were  ravaged,  and  the  whole  New 
England  coast  was  kept  in  terror  by  raiding  expe- 
ditions. This  bitter  experience  bore  fruit,  and  no 
sooner  had  the  war  ended  than  the  defence  of  the 
Atlantic  seaboard  was  seriously  taken  in  hand. 

In  1816  a  Board  of  Engineers  was  constituted  to 
examine  the  sea-coast  and  to  prepare  plans  for  defen- 
sive works,  subject  to  the  revision  of  the  Chief  of  En- 
gineers and  to  the  sanction  of  the  Secretary  of  War. 


Coast  Defence  in  America.  137 

This  important  Board,  which  at  the  outset  consisted 
of  General  Simon  Bernard,  Colonel  William  McRee, 
and  Lieutenant-Colonel  J.  G.  Totten,  may  justly  be 
said  to  have  originated  the  first  permanent  system  of 
coast  defence  on  this  continent.  Indeed,  at  that  date 
European  treatises  on  fortifications  scarcely  touched 
on  this  branch  of  the  subject,  so  little  was  science 
supposed  to  be  concerned  in  the  throwing-up  of  bat- 
teries to  contend  with  ships. 

Perhaps  no  better  idea  of  the  problem  before  the 
Board  of  Engineers  can  be  given  than  by  quoting 
the  language  of  a  contemporary  writer,  a  British  of- 
ficer who  had  taken  part  in  the  expedition  against 
Baltimore.     He  wrote : 

''America  must  be  assaulted  only  on  her  coasts. 
Her  harbors  destroyed,  lier  ship]3ing  burned,  and  her 
seaport  towns  laid  waste,  are  the  only  evils  she  has 
reason  to  dread.  ... 

''To  the  plan  proposed,  of  making  desert- the 
whole  line  of  coast,  it  may  be  objected  that  by  so  do- 
ing we  should  distress  individuals  and  not  the  gov- 
ernment. But  they  who  offer  this  objection  forget 
the  nature  both  of  the  people  whose  cause  they 
plead  and  of  the  government  under  which  they  live. 

"In  a  democratical  government  the  voice  of  the 
people  must  at  all  times  prevail.  The  members  of 
the  House  of  Representatives  are  the  very  persons 
who,  from  such  proceedings,  would  suffer  most  se- 
verely, and  we  all  know  how  far  private  suffering 
goes  to  influence  a  man's  public  opinions.  .  .  . 

"By  compelling  the  constituents  to  experience 
the  real  hardships  and  miseries  of  warfare  you  will 
compel  the  representatives  to  a  vote  of  peace.  .  .  . 
Burn  their  houses,  plunder  their  property,  block  up 
their  harbors,  and  destroy  their  shipping  in  a  few 
places,  arfd  before  you  have  time  to  proceed  to  the 
rest  you  will  be  stopped  by  entreaties  for  peace." 


138  Sea- coast  Fortresses. 

The  Board  of  Engineers,  in  a  report  dated  in  1826, 
gave  a  general  resume  of  the  principles  which  had 
guided  their  labors,  and  of  the  progress  which  had 
already  been  made.  I  shall  quote  two  sentences 
which  specially  relate  to  the  subject  now  under  con- 
sideration : 

''The  means  of  defence  for  the  seaboard  of  the 
United  States,  constituting  a  system,  may  be  classed 
as  follows :  First,  a  navy ;  second,  fortifications ; 
third,  interior  communications  by  land  and  water  ; 
and,  fourth,  a  regular  army  and  well- organized 
militia.  ..." 

"Fortifications  must  close  all  important  harbors 
against  an  enemy,  and  secure  them  to  our  military 
and  commercial  marine ;  second,  must  deprive  an 
enemy  of  all  strong  positions  where,  protected  by 
naval  superiority,  he  might  fix  permanent  quarters 
in  our  territory,  maintain  himself  during  the  war,  and 
keep  the  whole  frontier  in  perpetual  alarm  ;  third, 
must  cover  the  great  cities  from  attack  ;  fourth,  must 
prevent  as  far  as  practicable  the  great  avenues  of  in- 
terior navigation  from  being  blockaded  at  their  en- 
trances to  the  ocean  ;  fifth,  must  cover  the  coastwise 
and  interior  navigation  by  closing  the  harbors  and 
the  several  inlets  from  the  sea  which  intersect  the 
lines  of  communication,  and  thereby  further  aid  the 
navy  in  protecting  the  navigation  of  the  country ; 
and,  sixth,  must  protect  the  great  naval  establish- 
ments." 

We  will  now  consider  briefly  the  character  of  the 
individual  works  constructed  in  inaugurating  this 
conjprehensive  system. 

Ever  since  the  general  introduction  of  gunpowder 
into  warfare,  the  rule  has  been  recognized  that  no 
masonry  must  be  exposed  to  the  fire  of  land  guns ; 
but  this  rule  was  not  deemed  applicable  wllen  ships, 
themselves  much  more  vulnerable  than  stone  walls. 


Coast  Defence  in  America.  139 

carried  the  guns.  Moreover,  the  distinguishing  char- 
acteristic of  the  line- of -battle  ship  of  that  day  was 
her  enormous  concentration  of  fire.  To  reply  with 
equal  chances  of  success,  many  land  guns  were  de- 
manded ;  and  space  was  lacking  for  them  at  most 
sites,  unless  advantage  were  taken  of  the  facilities  to 
pile  tier  above  tier  afforded  by  a  masonry  scarp. 

The  use  of  the  casemate  in  flank  defence  may  be 
traced  back  to  the  early  part  of  the  sixteenth  cen- 
tury ;  but  the  Marquis  de  Montalembert,  writing  near 
the  close  of  the  eighteenth  centuiy,  had  lecently 
given  the  invention  an  extraordinary  development 
To  the  needs  of  sea-coast  fortification  casemates  were 
peculiarly  well  adapted,  and  he  had  presented  special 
designs  for  the  piirpose.  The  forts  constructed  to  de- 
fend the  roadstead  and  harbor  of  Cherbourg  in  1786 
were  patterned  after  these  designs  ;  and  other  Euro 
pean  nations  followed  in  the  same  track.  As  already 
stated.  Colonel  Williams  introduced  casemates  into 
this  country  by  the  construction  of  Castle  Williams 
and  sister  forts  in  1807 ;  and  the  Board  of  Engineers 
adopted  them  as  the  basis  of  the  permanent  system. 

Time  is  lacking  to  trace  the  development  of  that 
system,  and  the  successive  improvements  introduced 
by  General  Totten  during  the  construction  of  the 
works.  They  were  radical,  especially  as  to  the  de- 
tails of  the  embrasure ;  he  reduced  the  dangerous 
opening  from  28  square  feet  to  about  10  square  feet, 
and  this  with  an  increased  traverse  and  elevation  for 
the  gun.  He  was  also  the  first  to  introduce  iron  for 
defensive  purposes  into  sea-coast  forts.  This  innova- 
tion resulted  from  a  series  of  experiments  carried  out 
at  West  Point  between  the  years  1852  and  1855.  The 
throats  of  all  embrasures  constructed  after  1858  were 
reinforced  by  8-inch  wrought-iron  plates  set  into  the 
masonry  ;  and,  during  the  loading  of  the  guns,  the 
embrasure  openings  were  closed  by  iron  shutters  two 


140  Sea-coast  Fortresses. 

inches  thick  and  proof  against  the  largest  grape. 
There  is  one  sentence  in  General  Totten'  s  report  upon 
these  experiments,  dated  March,  1857,  which  is  pa- 
thetic as  showing  that  the  shadow  of  the  great  change 
about  to  occur  in  naval  warfare,  which  was  destined 
even  before  his  death  to  sweep  away  the  system  of 
forts  he  had  elaborated  by  the  labor  of  liis  wliole  life, 
had  made  itself  perceived.     He  wrote  in  1857 : 

"  Were  it  not  for  the  vastly  greater  cost,  the  whole 
scarp  might  be  faced  with  iron — indeed,  might  be 
made  of  iron  only ;  but,  until  there  shall  be  much 
stronger  reasons  than  now  exist,  or  are  now  antici- 
pated, for  believing  that  well-constructed  masonry 
batteries  may  be  breached  by  naval  broadsides,  the 
cheaper  construction  can  be  safely  followed — espe- 
cially as,  should  such  a  necessity  ever  arise,  they  may 
be  externally  plated  with  iron." 

The  actual  construction  of  works  upon  General 
Totten's  system  covered  a  period  of  45  years,  termi- 
nating about  a  year  before  the  close  of  the  civil  war. 
They  are  masonry  structures,  usually  placed  but  lit- 
tle above  the  water-level,  rising  into  one,  two,  or 
three  tiers  of  casemates  and  surmounted  by  a  tier  in 
barbette.  The  scarps  are  built  without  any  bonding 
of  the  masonry  into  the  supporting  piers  (which 
would  cause  unequal  settling  on  such  sites  as  most  of 
these  works  occupj^).  In  all  the  later  works  the 
scarps  of  the  water-fronts  are  8  feet  thick ;  where 
tliey  are  backed  by  the  piers  of  the  casemates  the  re- 
inforcement amounts  to  2%  feet ;  the  masonry  of  the 
casemate  arch,  above  the  level  of  the  communication 
arch,  extends  a  solid  support  to  the  whole  structure 
over  30  feet  thick  ;  immediately  in  front  of  the  guns, 
at  the  "  recess,"  there  is  a  small  space  where  the 
thickness  is  reduced  to  5  feet.  In  some  of  the  earlier 
works  the  casemate  arches  were  sprung  at  the  level 
of  the  barbette  tier  and  covered  four  guns  each,  the 


Coast  Defence  in  America.  141 

two  of  the  second  tier  resting  on  a  wooden  floor  ;  but 
all  the  later  scarps  are  solidly  backed  against  single 
arches.  In  plan  these  works  are  usually  hexagonal, 
often  truncated  on  the  land  side.  The  superiority  of 
the  hexagon  arises  from  its  permitting  the  casemate 
guns  on  adjacent  fronts  to  be  fired  in  parallel  planes 
at  their  extreme  traverse  (30  degrees).  This  covers 
and  prevents  a  dead  angle  at  the  salient  between 
them.  Where  there  is  a  barbette  tier,  the  guns,  ad- 
mitting of  a  traverse  of  60  degrees  from  the  front  in 
each  direction,  strongly  reinforce  the  fire  of  the  case- 
mate guns  over  this  naturally  weak  angle. 

So  soon  as  the  work  of  fortifying  the  coast  was 
resumed  after  the  civil  war  a  radical  change  of  sys- 
tem occurred.  Masonry  Avas  provisionally  aban- 
doned, and  earth  was  substituted  for  every  kind  of 
cover.  Under  this  system,  which  continued  until  ap- 
propriations ceased  in  1875,  many  batteries  were 
built  at  important  positions  ;  and  they  will  serve  a 
good  purpose,  notwithstanding  the  rapid  progress  in 
guns  which  has  occurred  since  they  were  built.  Af- 
ter 1870  these  earthen  batteries  were  constructed  to 
receive,  if  desired,  the  pattern  of  the  King  disaj^pear- 
ing  carriage  designed  for  the  15-inch  gun. 

All  the  sites  now  owned  by  the  United  States  suit- 
able for  the  erection  of  defensive  works,  contain 
specimens  of  the  different  types  just  described  ;  and 
it  is  therefore  a  live  question  what  shall  be  done 
with  them  when  work  is  resumed.  As  stated  in  a 
former  lecture,  many  of  the  old  masonry  forts,  with 
their  old  armament,  will  be  not  without  value  for  the 
necessary  flanking  of  the  submarine  mines  ;  and  the 
later  earthen  batteries  may  often  be  modified  to  re- 
ceive guns  of  the  new  type.  But  the  general  problem 
compels  the  consideration  of  a  subject  which  I  have 
heretofore  passed  over — the  relative  and  absolute  re- 
sistance opposed  by  different  kinds  of  materials,  such 
as  armor,  masonry,  and  earth,  to  modern  projectiles. 


142  Sea-coast  Fortresses. 

llESrSTAlS^CE   TO   PROJECTILES. 

Armor.— -The  armor  question  is  by  no  means  the 
same  for  land  fortifications  as  for  ships.  The  ele- 
ment of  weight,  so  important  when  displacement 
is  involved,  demands  far  less  consideration  when 
the  solid  earth  supplies  foundations.  The  ratio  be- 
tween resistance  and  weight  has  decided  the  matter 
for  naval  uses,  steel  or  comp.ound  armor  being  now 
universally  adopted.  The  decision  for  forts  is  still 
an  open  one.  Heretofore  Engineers  have  confined 
themselves  either  to  wrought  iron  or  to  the  Gruson 
chilled  cast  iron,  no  steel  or  compound  armor  having 
yet  been  used  or  strongly  advocated  for  use  in  coast- 
wise works. 

Wrought-iron  armor  localizes  the  injury  better 
than  steel  or  compound  armor,  and  thus  saves  the 
general  structure ;  the  Gruson  metal  breaks  up  and 
deflects  the  projectile,  and  absorbs  the  remaining  en- 
^^^Y  by  so  large  a  mass  that  its  strength  to  receive 
farther  shocks  is  often  not  seriously  impaired.  Cap- 
tain Bixby,  Corps  of  Engineers,  in  a  recent  official 
report  upon  duties  which  had  been  assigned  to  him 
in  Europe,  sums  up  the  case  in  what  I  regard  as  a 
fair  statement,  except  perhaps  that  he  lays  hardly 
enough  stress  upon  the  fact  that  chilled  cast  iron 
does  not  admit  of  subsequent  thickening,  while  the 
other  kinds  may  readily  be  reinforced  if  necessary. 
He  states : 

'^  At  the  present  date  heavy  armor  (from  12  to 
40  inches  thick)  is  very  expensive,  its  cost,  firmly 
mounted  in  place,  being  approximately  as  follows  : 
wrought  iron,  from  $200  to  $350  per  ton  ;  steel-faced 
wrought  iron  or  surface-hardened  steel,  from  $400  to 
$600  per  ton  ;  chilled  cast  iron,  from  $150  to  $200  per 
ton.  .  .  . 

*' Taking  into  consideration  the  cost  of  bolts, 
bolt-holes,  and  other  means  of  assemblage,  and  the 


Resistance  to  Projectiles.  143 

cost  of  fitting  and  setting  up  the  armor,  the  same 
amount  of  money  will,  roughly  speaking,  furnish  a 
steel-faced  wrought- iron  or  surface-hardened  steel 
armor  of  20  inches  thickness,  a  wrought-iron  armor 
of  40  inches  thickness,  or  a  chilled  cast-iron  armor  of 
60  inches  thickness.  E-ouglily  speaking,  the  steel- 
faced  wrought  iron  or  surface-hardened  steel  is  least 
heavy,  the  strongest  in  proportion  to  its  thickness  ; 
the  wrought  iron  is  easiest  to  make,  easier  worked, 
easier  added  to,  best  against  racking  shots,  localizes 
best  the  effect  of  a  shot,  can  best  be  penetrated  and 
even  perforated  without  being  actually  destroyed, 
and  can  best  have  the  amount  of  penetration  calcu- 
lated in  advance  ;  the  chilled  cast  iron  is  easiest  and 
quickest  made,  can  be  given  any  shape,  requires  the 
least  working,  is  easiest  and  quickest  placed  in  posi- 
tion, is  never  penetrated,  always  shivers  in  pieces  the 
striking  projectiles,  generalizes  best  the  effect  of  a 
striking  projectile,  provides  the  greatest  weight  or 
mass  to  receive  the  total  living  force  of  the  striking 
projectile,  has  no  bolts  to  be  knocked  off  on  its  inte- 
rior, and  sends  off  the  fewest  splinters  on  its  interior. 
The  steel  has  undoubtedly  the  advantage  around  the 
edge  of  embrasures,  and  wherever  thickness  or 
weight  is  undesirable  or  inadmissible,  also  wherever 
it  can  be  backed  by  a  great  thickness  of  less  expen- 
sive masonry  ;  the  chilled  cast  iron  has  undoubtedly 
the  advantage  .  .  .  .wherever  weight  or  mass  is  an 
advantage ." 

In  the  matter  of  bolts,  wrought-iron  armor  re- 
quires one  to  each  10  or  12  square  feet  of  surface  ; 
compound  or  steel  armor  requires  one  to  each  four 
square  feet  of  surface ;  chilled  cast  iron  dispenses 
with  bolts  entirely. 

Wrought-iron,  steel,  and  compound  or  steel-faced 
armor  are  so  familiar  to  naval  officers  that  no  time  will 
be  given  to  their  further  discussion.    Gruson  chilled 


144  Sea-coast  Fortresses. 

casfc  iron,  being  inapplicable  to  floating  structures,  is 
probably  less  studied,  and  the  following  short  ex- 
tracts from  a  publication  by  Julius  von  Schutz,  En- 
gineer of  Gruson's  Works,  which  has  just  left  the 
press,  may  perhaps  be  not  uninteresting : 

*^  The  Gruson  chilled  cast  iron  is  a  mixture  of  dif- 
ferent blends  of  pig-iron,  cast  in  chill,  to  which  it  owes 
its  hardness. 

"  In  accordance  with  the  two  chief  qualities  whicli 
he  sought  to  obtain,  Gruson  chose  two  sorts  of  pig- 
iron  for  his  principal  materials,  each  of  which  pos- 
sessed one  of  the  desired  qualities — a  highly  carbon- 
ized steel-hard,  white  iron,  and  a  soft  gray  iron. 

''Although  it  appeared  impossible,  by  the  mere 
mixture  of  the  two  metals,  to  combine  hardness  and 
toughness  in  the  same  stratum  of  iron,  another  way 
of  solving  the  problem,  to  produce  a  hard  surface  on 
a  soft,  elastic  interior,  seemed  less  difficult  if  it  were 
possible  to  combine  the  two  different  materials  to- 
gether with  such  a  gradual  change  of  their  respective 
properties  that  no  marked  line  of  separation  should 
occur ;  and  this  is  tlie  problem  which  Gruson,  after 
years  of  effort,  succeeded  in  reaching  in  such  a  man- 
ner that  even  at  the  present  day  his  chilled  cast  iron 
possesses  a  superiority  over  that  of  other  makers. 

''  Gruson  attained  his  object  by  a  seemingly  simple 
procedure.  By  the  use  of  iron  forms,  or  moulds  for 
casting,  he  prevented,  by  a  rapid  cooling  of  the  surface, 
the  always  existing  tendency  in  a  fluid  casting  for 
the  carbon  to  separate  off  in  scales  of  graphite. 

''  It  would  be  foreign  to  the  scope  of  this  compila- 
tion to  specify  the  details  of  the  manufacture  of  the 
chilled  cast  iron,  and  we  will  only  describe  the  peculiar 
structure  which  characterizes  the  broken  section  of  a 
piece  of  the  Gruson  chilled  cast  iron.  The  exterior 
layer  is  of  a  flne  fibrous  character,  which  passes,  with- 
out visible  lines  of  separation,  into  the  granular  s true- 


Resistance  to  Projectiles,  145 

ture  of  tlie  so-called  mottled  iron,  which  in  tnrn 
gradually  assumes  the  character  and  line  crystalline 
structure  of  the  gray  soft  iron.  This  is  the  great  dif- 
ference which  distinguishes  Gruson  chilled  cast  iron 
from  tliat  of  other  manufacturers,  in  whose  iron  the 
line  of  separation  of  the  layers  is  always  more  or  less 
distinctly  marked,  and  the  edge  between  the  hard  and 
soft  metal  visibly  seen.  .  .  . 

''To  his  plates  he  gave  a  curved  form,  which  in 
vertical  section  approaches  that  of  a  quadrant  of  an 
ellipse.  Such  a  surface,  by  its  hardness,  deflected  the 
shot  striking  it,  and  besides  it  possessed  this  advan- 
tage, that,  by  reason  of  their  arched  form,  the  plates 
supported  one  another  and  retained  their  position  by 
their  weight,  without  the  necessity  of  securing  them 
by  bolts." 

I  have  already  shown  that  it  would  be  unwise  to 
devote  the  first  funds  granted  by  Congress  for  coast 
defence  to  the  purchase  of  armor  of  any  kind  ;  it  is 
certain  that  whatever  is  purchased  must  be  manufac- 
tured in  this  country;  the  facilities  for  working  heavy 
masses  here  are  steadily  increasing  ;  the  struggle  be- 
tween the  different  kinds  of  armor  has  not  ceased  in 
Europe;  and  when  the  time  conies  for  purchasing,  the 
choice  may  be  affected  by  conditions  materially  dif- 
ferent from  those  now  existing.  For  these  reasons 
the  Corps  of  Etigineers  has  never  committed  itself  to 
a  definite  choice.  We  know  that  wrought-iron  armor 
8  feet  wide,  10  inches  thick,  and  weighing  from  10  to 
12  tons  can  now  be  rolled  in  this  country;  that  larger 
plates  could  soon  be  fabricated  were  there  any  de- 
mand for  them;  that  probably  the  same  will  soon  be 
true  for  steel,  and  that,  if  sufficient  inducements  were 
offered,  works  for  making  the  Gruson  chilled  cast  iron 
would  be  quickly  established.  In  my  judgment, 
therefore,  it  is  the  part  of  wisdom  for  us  in  this  mat- 
ter to  say  with  the  Russians  :  "  I  sit  upon  the  bank 
and  there  I  await  the  wind." 


146  Sea-coast  Fortresses. 

Masonry. — Very  few  experiments  have  been  made 
to  determine  the  penetration  of  modern  ordnance  in 
masonry. 

In  1877  an  unfilled  Palliser  shell  was  fired  from  a 
12.5-inch  38-ton  gan  at  a  mass  of  masonry  at  Shoe- 
buryness.  The  projectile  weighed  800  pounds,  its 
striking  velocity  was  1  405  feet,  and  its  energy  10  080 
foot- tons.  The  masonry  was  an  old  experimental 
casemate,  somewhat  shaken  by  previous  firing ;  it 
was  16  feet  by  12  feet  by  16  feet  liigh.  The  shell,  after 
passing  through  6.5  feet  of  granite  and  Q.Q  feet  of 
brick  and  Portland  cement  concrete,  was  found  on  the 
floor  of  the  casemate.  The  wall  was  completely 
wrecked. 

In  1881  the  cast-iron  100-ton  gun  made  in  Italy 
was  fired  at  a  steep  rock  face.  The  projectile,  vveigli- 
ing  2  200  pounds  and  striking  with  a  velocity  of  1  456 
feet,  had  an  energy  of  about  32  000  foot- tons.  The 
penetration  was  over  20  feet. 

A  concrete  butt  at  Dungeness  was  fired  at  with 
smaller  ^projectiles  in  1881.  The  concrete  had  been 
made  of  rounded  shingle  about  two  years  before,  and 
was  not  so  solid  as  if  the  material  had  been  more 
angular.  The  following  were  the  maximum  penetra- 
tions, the  energies  being  respectively  5  738,  1  989,  and 
1  555  foot-tons : 

A  10-inch  M.  L.  rifle  of  18  tons :  Palliser  shell, 
17  feet ;  common  shell,  13.8  feet. 

A  6-inch  B.  L.  rifle  of  80  cwt.:  Palliser  shell,  12.6 
feet ;  common  shell,  10.8  feet. 

A  6.6-inch  M.  L.  rifle  of  70  cwt.:  Palliser  shell, 
8.2  feet ;  common  shell,  8.4  feet. 

In  1883  a  muzzle-loading  80- ton  gun  was  flred  at  a 
masonry  target  at  Shoeburyness  built  for  the  pur- 
pose. The  projectile  was  chilled  cast  iron,  1  700 
pounds  in  weight.  The  striking  velocity  was  1  580 
feet  per  second,  giving  an  energy  of  about  30  000 
foot-tons.     There  are  some  discrepancies  in  different 


Resistance  to  Projectiles,  147 

statements  respecting  the  details  of  this  experiment. 
I  was  informed  on  the  spot  a  few  days  after  the  tiring 
that  the  shot  passed  through  9  feet  of  granite,  6  feet 
of  good  Portland  cement  concrete,  and  tlien  encoun- 
tered a  brick  wall  5  feet  thick,  the  whole  forming  one 
solid  wall,  backed  by  buttresses  of  concrete  20  feet 
thick.  The  brick  wall  deflected  the  shot  from  its 
course,  and  it  curved  to  the  right  and  finally  to  the 
front,  after  passing  over  a  total  distance  of  about  25 
feet.     The  shot  broke  up. 

Another  similar  shot  was  fired  at  a  mass  of  Port- 
land cement  concrete  about  40  feet  thick,  made  about 
9  months  before.  The  penetration  was  32  feet  (Cap- 
tain Lewis,  R.E.,  says  34  feet)  on  a  straight  course  ; 
the  mass  was  also  badly  cracked. 

Another  similar  shot  was  fired  at  a  compound 
plate  of  steel-faced  wrought  iron,  12  inches  thick, 
secured  without  any  elastic  backing  to  a  masonry 
mass  20  feet  thick,  like  that  first  described.  The  shot 
bulged  and  just  penetrated  the  plate,  so  that  its  j^oint 
appeared  at  the  back,  and  the  injury  to  the  masonry 
was  insignificant. 

Another  similar  shot  was  fired  at  a  wrought-iron 
sandwich  target  backed  in  the  same  manner.  The 
target  consisted  of  two  8-inch  plates,  separated  and 
backed  by  5  inches  of  wood.  The  shot  traversed  the 
shield  and  granite,  resting  at  the  concrete  just  behind 
it  (penetration,  16  inches  of  iron,  10  inches  of  wood, 
and  9  feet  of  masonry). 

In  1884  the  12-inch  43-ton  gun  was  fired  at  the  same 
target  at  Shoeburyness,  which  had  been  repaired  for 
the  purpose.  Captain  Lewis,  R.E.,  states  that  it 
now  consisted  of  14  feet  of  granite  and  Portland 
stone,  2  feet  of  Portland  cement  concrete,  and  6  feet 
of  brick.  The  shot  weighed  715  pounds,  its  striking 
velocity  was  1  804  feet  per  second,  and  its  energy 
16  300  foot-tons.  The  penetration  was  11.3  feet,  and 
the  granite  was  much  shattered  and  displaced. 


148  Sea-coast  Fortresses, 

In  firing  at  the  concrete  butt  with  this  gun,  the 
striking  velocity  was  reduced  to  1  524  feet  per  second, 
giving  an  energy  of  11  620  foot-tons.  The  penetra- 
tion was  24  feet,  and  a  large  mass  2  feet  thick  flaked 
off  from  the  front. 

The  two  8  inch  wrought-iron  plates  used  as  a  fac- 
ing, attacked  by  the  same  gun,  reduced  the  penetra- 
tion in  the  granite  to  5.9  feet. 

A  mass  of  concrete  17  feet  thiclv  was  faced  by 
three  1-inch  plates  of  wrought  iron  and  backed  by 
the  granite  wall.  The  result  with  the  43-ton  gun  was 
unsatisfactory,  the  concrete  disintegrating ;  ba<t  Gen- 
eral Inglis,  K-.E.,  states  that  the  latter  was  not  prop- 
erly set. 

Captain  Lewis,  E..E.,  gives  the  following  as  the 
results  derived  from  the  firing  at  the  bombardment  of 
Alexandria:  ''The  maximum  x>enetration  of  blind 
shell,  9-inch  or  lO-inch,  into  the  soft  rubble  scarp  of 
Fort  Adda,  was  from  8  to  9  feet.  A  9-inch  Palliser 
burst  with  4  feet  penetration.  A  16-inch  common 
shell  burst  with  8  feet  6  inches  penetration,  and  made 
a  crater  about  10  feet  in  diameter  at  the  face  of  the 
wall.  This  was  one  of  the  best  results  obtained.  The 
shell  struck  near  the  base  of  the  wall.  Range  about 
1  500  yards. 

''At  Fort  Pharos  the  10-inch  shell,  common  and 
Palliser,  penetrated  the  8-foot  rubble  walls  of  the 
casemates  and  burst  inside." 

Comparing  these  results  with  those  of  former  fir- 
ing with  less  powerful  guns,  and  allowing  for  the 
reduced  effect  of  the  ranges  likely  to  be  used  in  war, 
it  appears  that  not  less  than  30  feet  of  good  granite 
masonry,  or  40  feet  of  good  concrete  masonry,  is  ad- 
missible in  sea-coast  forts  where  it  is  to  be  exposed 
to  direct  fire,  and  that  even  these  thicknesses  are  not 
sufficiently  great  to  resist  a  prolonged  bombardment. 
English  engineers  now  protect  their  magazines  wftth 


llesistance  to  Projectiles.  149 

40  feet  of  masonry,  but  an  increased  thickness  is  an- 
ticipated. 

Resistance  of  Earth. — The  resistance  of  earth 
to  penetration  of  modern  ordnance  is  so  variable,  not 
ordy  from  difference  of  consistency  but  also  from  the 
tendency  of  the  projectile  to  change  direction  and 
pass  out  at  the  top  of  the  parapet,  that  it  is  not  easy 
to  frame  a  rule  for  suitable  thickness.  Clay  opposes 
a  local  resistance  like  wrought  iron  ;  sand  seems  to 
wedge  in  front  and  thus  resists  as  would  a  cone 
pressed  at  the  vertex.  This  difference  is  marked  and 
characteristic,  and  preference  should  therefore  al- 
ways be  given  to  sand  where  it  can  be  obtained  at 
reasonable  expense.  The  tendency  to  curve  upward, 
always  present,  appears  to  increase  with  the  range — 
possibly  because  the  velocity  of  fall  continues  at  the 
base  after  the  point  is  engaged.  However  this  may 
be,  the  fact  occasioned  much  surprise  at  the  bom- 
bardment of  Alexandria,  where  no  x)rojectile,  even 
those  of  the  80-ton  gun,  penetrated  the  sand  parapet 
to  a  greater  depth  than  20  feet  before  coming  out  at 
the  top. 

Firing  at  Fort  Monroe  in  1866-67  with  a  M.  L.  12- 
iuch  rifled  gun,  with  projectiles  varying  from  500  to 
600  pounds  in  weight,  and  velocities  ranging  from 
1  100  to  1  300  feet  per  second,  indicated  that  penetra- 
tions should  not  be  estimated  at  less  than  20  feet. 

The  Italian  100-ton  gun  (cast  iron)  was  fired  at  a 
sand  parapet  in  1880-1,  the  projectile  weighing  2  200 
pounds,  the  striking  velocity  being  1  453  feet,  and  the 
energy  being  32  000  foot-tons.  The  penetration  in 
five  shots  varied  between  39  and  47  feet.  One  of 
their  10-incli  guns  at  a  range  of  1  100  yards  gave  a 
penetration  of  24  feet  into  earth  or  20  feet  into  sand. 

At  Woolwich,  in  1880,  the  12-inch  M.  L.  rifled  gun 
gave  a  maximum  penetration  of  6Q  feet  in  sand. 
Older  experiments  at  Shoeburyness,  with   a  butt  of 


150  Sea- coast  Fortresses. 

stiff  marsh  clay,  gave  as  a  mean  penetration  of  23 
shots  with  a  13.3-inch  rilled  gun,  36.5  feet,  the  maxi- 
mum being  50  feet ;  and  as  a  mean  penetration  of  43 
shots  with  a  9.2-inch  rifled  gun,  32  feet,  the  maximum 
being  40  feet. 

The  rule  given  by  Captain  Lewis,  R.E.,  in  1882, 
as  the  result  of  English  trials  with  siege  artillery  of 
the  present  type,  is  that  the  extreme  j^enetration  of 
earth  in  feet  is  about  four  times  the  calibre  in  inches. 

In  the  Lydd  experiments  of  18S5  two  shots  were 
fired  with  a  9.2-inch  B.  L.  gun,  at  a  range  of  1  200 
yards,  against  a  clay  parapet  30  feet  thick  with 
an  exterior  slope  of  45  degrees.  The  first  shot  pene- 
trated 13  feet  into  the  parapet ;  the  second  went 
through,  lowering  the  interior  crest  3.5  feet.  About 
61.9  cubic  yards  were  removed.  No  such  results  were 
obtained  with  sand,  or  with  a  loam  consisting  of 
two  parts  sand  and  one  part  clay. 

The  U.  S.  Board  of  Engineers,  making  allowance 
for  probable  increased  calibres  and  for  craters  which 
may  be  expected  in  action,  have  adopted  70  feet  be- 
tween crests  as  the  proper  thickness  to  be  given  to 
sand  parapets,  although,  in  view  of  the  facts  above 
stated,  the  probability  of  penetration  with  a  less 
thickness  would  not  appear  to  be  sufficiently  great  to 
require  all  old  parapets  to  be  increased  to  this  stan- 
dard. 

APPROXIMATE    FOEMUL^. 

When  planning  and  studying  sea-coast  fortresses 
a  few  rules,  in  a  form  to  be  easily  remembered,  are 
convenient  to  assist  in  roughly  estimating  the  proba- 
ble effect  of  tiring. 

Such  are  : 

For  Weight  of  Projectiles. — The  cube  of  the 
radius  in  inches  gives  the  weight  in  pounds  of  the 
solid  spherical   projectile.      Modern  armor-piercing 


Approximate  FormidcB.  151 

projectiles  usually  range  from  8.3  to  4  times  this 
weight.  Another  form  of  this  rule  (corresponding  to 
a  multiplier  of  4)  is  to  take  half  the  cube  of  the  cali- 
bre of  the  gun  in  inclies  for  the  weight  in  pounds. 

For  Velocity  of  Projectiles  of  High-Power 
Guns. — A  cliarge  of  one-fourth  of  the  weight  of  the 
projectile  will  give  a  velocity  of  about  1  500  or  1  600 
feet  per  second  ;  and  a  charge  of  one-half  that  weight, 
a  velocity  of  about  2  000  or  2  100  feet  per  second. 
These  are  muzzle  velocities ;  to  estimate  striking 
velocities  up  to  a  range  of  about  6  000  yards  subtract 
from  them' one- tenth  of  the  range  in  yards  ;  for  longer 
ranges  the  loss  is  less  rapid. 

For  Energy  in  Foot-Tons.— Take  seven-mil- 
lionths  of  the  product  of  the  square  of  the  velocity 
in  feet  by  the  weight  of  the  projectile  in  pounds. 

For  Penetration  of  Wrouglit-Iron  Plates. — 
Under  favorable  service  conditions,  the  thickness  in 
inches  of  wrought-iron  armor  pierced  by  a  suitable 
projectile,  may  be  estimated,  with  about  as  much  pre- 
cision as  the  subject  admits,  by  taking  one-thou- 
sandth of  the  product  of  the  calibre  in  inches  by  the 
velocity  of  the  projectile  in  feet  per  second.  This 
rule,  suggested  by  Captain  Orde  Browne,  R.A.,  de- 
pends for  its  accuracy  upon  the  constancy  of  the 
ratio  between  the  weight  of  the  spherical  shot  and  of 
the  elongated  projectile  of  the  same  calibre.  It  is  not 
far  from  true  in  ordinary  practice  with  armor-pierc- 
ing projectiles.  Common  shells  can  be  put  through 
wrought-iron  plates  about  half  a  calibre  thick. 

For  Limit  of  Resistance  of  Steel-Faced  and 
Steel  Armor. — The  compound  plates  and  steel 
plates  now  manufactured  mnst  be  disruj^ted  rather 
than  perforated  ;  and  their  extreme  resistance  (not 
materially  different  for  these  two  kinds  of  armor)  is 
usually  estimated  in  terms  of  the  thickness  of 
wrought  iron  which  opposes  an  equivalent  resistance 


152  Sea-coast  Fortresses. 

to  perforation.  This  has  been  shown  by  many  trials 
to  vary  between  one-quarter  and  one-half  greater 
thickness,  the  latest  accepted  value  being  one-third 
greater  thickness — i.e.,  a  9  inch  steel  or  compound 
plate  is  equivalent  to  a  12-iiich  wrought-iron  plate, 
since  a  projectile  which  will  perforate  the  latter  will 
usually  disrupt  the  former.  It  must  not  be  forgot- 
ten, however,  that  much  depends  upon  the  projectile 
itself.  When  the  latter  is  broken  up  by  the  shock 
its  work  on  the  plate  is  greatly  and  irregularly  re- 
duced ;  and  until  quite  recently  this  rupture  ap- 
peared to  be  unavoidable  with  very  hedvy  armor. 
Within  a  year,  'however,  a  16.5-inch  St.  diamond 
steel  battering  shell,  with  a  striking  velocity  of  only 
1  410  feet  per  second  and  an  energy  of  only  about 
24  000  foot-tons,  traversed,  entire,  a  19.7-inch  Creusot 
steel  armor-plate,  and  fell  400  metres  beyond  it, 
upset  one-quarter  of  an  inch  !  Also  12-inch  Holtzer 
projectiles  have  penetrated  16-inch  compound  plates 
practicall}^  uninjured. 

There  is  little  utility  in  attempting  to  construct  a 
formula  to  predict  the  effect  of  the  imp)act  of  so  di- 
verse projectiles  as  have  been  used  in  firing  at  steel 
and  compound  armor,  but  I  fin(^  the  results  of  many 
of  the  experiments  to  be  fairly  represented  by  the 
following  rule  :  A  steel  or  compound  plate  with  ordi- 
nary backing  rarely  fails  to  yield  to  a  projectile  hav- 
ing an  energy  in  foot-tons  represented  by  sixty  times 
the  square  of  its  thickness  in  inches. 

For  Resistance  of  Chilled  Cast  Iron.— No  for- 
mula for  the  resistance  of  this  kind  of  armor  has 
been  generally  accepted.  Gruson's  rule  for  the  maxi- 
mum thickness  in  inches  to  be  given  to  his  plates  is 
the  product  of  a  constant  by  the  fourth  root  of  the 
energy  in  foot-tons  to  which  it  is  to  be  exposed.  His 
constants  are  :  For  port-plates  0.29  ;  for  side-plates, 
0.27 ;  for  glacis-plates  with  earth  in  front,  0.22 ;  and 


Fortijication  of  the  Site  Selected,  153 

for  glacis-plates  with  granite  in  front,  0.20.  For  in- 
land fortifications  tliese  constants  are  increased  ten 
per  cent. 

FORTIFICATEON   OF   THE   SITE   SELECTED. 

Coast  defences  differ  radically  from  ordinary  for- 
tifications, in  that  tliey  are  not  expected  to  resist  an 
attack  by  formal  land  approaches.  They  must  be 
planned  to  resist  capture  by  surprise  or  by  storm, 
but  not  by  regular  saps.  Moreover,  our  sea-coast 
fortresses  of  to-day  will  be  much  less  exposed  to 
boat  attack  than  were  those  planned  in  1816.  Not 
only  lias  the  increase  of  population  and  the  exten- 
sion of  railroad  and  telegraphic  communication  ren- 
dered it  vastly  more  easy  to  concentrate  reinforce- 
ments, but  the  reduction  of  crews  in  naval  v^ar-ships 
has  lessened  the  force  available  for  landing  opera- 
tions. 

For  these  reasons  the  idea  of  constructing  a  fort- 
ress to  contain  all  the  water-bearing  guns  within  its 
enceinte  has  long  been  abandoned.  The  ordnance  is 
now  distributed  in  detached  batteries,  each  provided 
with  minor  defensive  arrangements  suited  to  the 
locality,  while  the  whole  position  is  made  secure  by 
a  central  keep.  This  'is  usually  a  small  enclosed 
work,  fortified  on  the  principles  recognized  in  land 
constructions.  It  should  be  concealed  from  the  view 
of  hostile  shipping  ;  should  contain  or  flank  the 
casemate  for  operating  the  submarine  mines ;  and 
should  command  as  many  of  the  detached  batteries 
as  the  site  will  permit. 

Four  kinds  of  fire  are  requisite  to  contend  against 
a  modern  fleet :  (1)  A  sufficient  array  of  armor-pierc- 
ing guns  to  attain  the  vital  parts  behind  a  belt  of 
steel  about  20  inches  thick,  at  ranges  of  1  500  to 
2  000  yards.   (2)  Guns  throwing  large  common  shells 


154  Sea- coast  Fortresses. 

to  destroy  the  upper  works,  which  in  the  more  recent 
types  include  an  area  so  much  larger  than  the  ar- 
mored belt  that  this  kind  of  fiie  is  the  most  effective 
at  ranges  exceeding  2  000  yards.  High-power  guns 
of  moderate  calibres,  or  even  a  less  efficient  armament, 
will  serve  this  purpose.  Rapidity  of  fire,  calling  for 
many  guns,  is  needful.  Here  the  use  of  high  explo- 
sives in  shells,  which  (if  not  now)  is  certain  to  be  soon 
available,  will  play  its  most  important  part.  (3)  Ver- 
tical lire  from  heavy  mortars,  to  attack  the  lightly 
armored  decks  at  ranges  exceeding  1  500  yards  ;  and 
(4)  Light  guns,  inclading  machine  and  mpid-firing 
guns  as  well  as  the  old  types  throwing  canister, 
shrapnel,  and  shells,  to  flank  the  submarine  mines, 
repel  boat  attacks,  and  contend  with  the  torpedo- 
boat  armament  of  the  ships  if  they  can  approach 
sufficiently  near  to  bring  it  into  play  to  annoy  the 
cannoniers  in  serving  our  high-power  guns.  At  long 
ranges  machine-gun  fire  is  useless  because  its  effect 
cannot  be  noted. 

No  precise  rules  can  be  laid  down  for  fixing  the 
relative  proportions  of  these  different  types  in  a  mod- 
ern armament ;  the  engineer  must  study  his  special 
problem  and  be  governed  by  local  conditions.  In 
little  else  can  his  professional  skill  be  better  dis- 
played. The  principles  which  should  determine  the 
number  of  battering  guns  and  their  largest  calibres, 
have  already  been  considered. 

In  planning  the  works  the  chief  objects  are :  to 
dispose  separate  gun  batteries  in  such  a  manner  as 
to  cover  the  field  of  fire  thoroughly  without  leaving 
dead  angles,  and  to  permit  effective  concentration 
upon  the  more  important  channels  ;  to  place  the 
mortar  batteries  where  they  will  be  concealed  as  much 
as  possible  from  view,  and  where  their  smoke  shall  not 
interfere  with  the  guns ;  to  locate  the  submarine 
mining  casemates  where  they  will  be  secure  against 


Fortification  of  the  Site  Selected.  155 

bombardment ;  and,  finally,  to  make  the  needful  pro- 
visions against  surprise  by  boat  parties. 

The  separate  batteries  will  be  much  more  scat- 
tered than  formerly — partly  to  avoid  mutual  interfer- 
ence by  smoke,  which,  being  dependent  on  the  amount 
of  powder  burned,  will,  unless  provided  against,  be  a 
more  serious  annoyance  than  ever  before  ;  and  partly 
to  x)i'event  the  enemy  from  obtaining  that  concentra- 
tion of  fire  which  his  reduced  number  of  guns  will 
render  more  than  ever  desirable.  The  new  phases  of 
modern  warfare  have  thus  introduced  a  dispersed 
order  in  sea- coast  batteries  as  well  as  in  the  shock  of 
armies  in  the  field. 

Machine  guns  will  play  an  important  part  in  de- 
fending such  a  system  of  works  against  assault. 
They  concentrate  within  a  small  space  the  fire  of 
whole  regiments  under  the  old  system  ;  they  may  be 
withdrawn  from  view,  and  be  made  safe  from  cap- 
ture, at  small  expense  ;  and,  lastly,  they  avoid  the  ne- 
cessity of  providing  bomb-proof  quarters  for  a  large 
garrison.  Still  a  reserve,  in  moderate  numbers,  is  a 
necessity  ;  and  provision  for  cover  during  bombard- 
ment, and  a  strong  keep  to  serve  as  a  rallying  point 
in  case  of  a  formidable  attack,  wdll  form  a  part  of 
every  important  sea-coast  fortress  of  to-day.  Trous 
de  loups,  wire  entanglements,  ordinary  arrangements 
for  ditch  defence,  etc.,  will  of  course  be  provided  ac- 
cording to  local  needs,  but  works  of  this  character 
will  be  largely  left  to  be  placed  by  the  garrison  so 
soon  as  war  is  declared. 

Before  a  fortress  can  be  planned  some  definite  es- 
timate must  be  formed  as  to  the  size  of  its  war  gar- 
rison. The  rule  abroad  is  to  determine  the  number  of 
cannoniers  needful  to  serve  all  the  guns  likely  to  be 
in  action  at  the  same  time,  and  the  number  of  the 
guards  ;  to  allow  three  reliefs  for  these  duties,  and  to 
the  total  thus  found  add  the  number  of  men  proba- 
bly to  be  detailed  on  special  duties. 


156  Sea- coast  Fortresses. 

Sucli  a  garrison  would  be  much  larger  than  would 
be  available  in  this  country  without  reinforcements 
of  volunteers  ;  and  in  general  it  should  be  ample  to 
defend  the  works  against  boat  attacks,  which  usually 
could  not  be  effectively  supported  by  the  iire  of  the 
fleet  at  the  moment  of  assault.  Provision  for  quar- 
tering such  a  garrison  will  therefore  suffice  in  plan- 
ning the  defences. 

To  determine  the  lines  of  the  batteries  wdiich,  in 
whole  or  in  part,  constitute  the  general  trace  of  the 
works,  the  following  is  the  usual  procedure.  Circles 
are  drawn  on  the  map,  with  the  battery  under  consid- 
eration as  a  centre.  The  bounding  radii  of  fire  will 
be  determined  by  the  width  of  field  open  to  occu- 
pation by  the  fleet  ;  and  if  this  differs  materially  at 
tlie  different  pi  acticable  ranges,  separate  studies  must 
be  made  and  the  best  compromise  be  effected.  Each 
mode  of  mounting  has  a  maximum  angle  of  distribu- 
tion of  fire — a  revolving  turret  has  360  degrees,  a 
casemate  60  degrees,  an  ordinary  barbette  120  de- 
grees, etc.  If  the  desired  bounding  radii,  fixed  as  al- 
ready explained,  include  a  less  angle  than  that  per- 
mitted by  the  selected  mode  of  mounting,  the  crest  of 
the  battery  will  be  a  straight  line  perpendicular  to 
the  bisecting  radius  ;  if  not,  the  crest  should  be  a 
broken  line — and  in  general  an  angle  of  about  60  de- 
grees will  be  most  advantageous.  With  casemates 
this  angle  is  decidedly  the  best.  Having  drawn  the 
crest-line  upon  the  map,  note  whether  or  not  it  is  ex- 
posed to  be  flanked  or  enfiladed  by  shipping,  and  ex- 
amine the  locality  itself  to  learn  whether  a  slight 
change  of  position  would  reduce  the  cost  of  construc- 
tion. The  different  batteries  are  thua  successively 
established. 

The  traverses  and  parados  are  next  to  be  con- 
sidered, Traverses  are  desirable  between  all  large 
high-power  guns  mounted  in  barbette  :  (1)  to  sux)ply 


Fortification  of  the  Site  Selected.  157 

magazines  and  sliell  or  loading  rooms  ;  (2)  to  prevent 
the  blast  of  adjacent  j:>ieces  from  interfering  with 
each  other  ;  (3)  to  limit  the  effect  of  an  exploding 
shell ;  (4)  to  cover  the  guns  against  enfilade  fire,  if 
that  be  practicable  from  the  water.  On  the  other 
hand,  if  raised  considerably  above  the  level  of  the 
parapet,  as  has  usually  been  the  custom,  they  serve 
to  define  the  exact  position  of  the  gun  to  the  enemy  ; 
and,  with  the  increased  precision  of  fire  to  be  ex- 
pected from  shipsf,under  favorable  conditions,  this  is 
a  serious  objection.  Some  of  the  reasons  for  their 
existence  do  not  absolutely  compel  them  to  be 
raised  much  above  the  crest  of  the  parapet,  and  per- 
liaps,  where  there  is  no  danger  of  enfilade,  future 
practice  may  limit  them  to  that  height.  With  dis- 
appearing guns,  especially,  this  would  reduce  the 
target  to  a  long,  ill-defined  line  with  nothing  to  indi- 
cate their  position  except  an  occasional  appearance 
at  the  moment  of  firing. 

Recent  difiicalties  which  have  arisen  in  respect  to 
the  x)arados  are  more  perplexing.  Its  only  raison 
d'etre  is  to  afford  protection  against  reverse  fire,  to 
which  coast  batteries  are  sometimes  unavoidably  ex- 
posed. No  one  has  ever  proposed  to  use  the  device 
unnecessarily,  because  when  a  projectile  is  coming 
over  the  parapet  a  highway  to  speed  the  parting 
guest  is  an  instinctive  provision.  But  experiment 
lias  shown  that  even  when  parados  are  unavoidable  it 
it  is  not  easy  to  fulfil  the  conflicting  conditions  they 
impose.  Allowing  for  an  angle  of  fall  of  15  degrees, 
a  parados  must  be  placed  quite  near  the  gun  or  else 
be  built  to  an  excessive  height.  But  if  it  be  built  too 
near,  the  effect  of  shells  from  the  front,  of  the  size 
now  employed  by  ships,  is  disastrous.  Quantities  of 
earth,  especially  .if  frozen,  stones,  gravel,  and  splin- 
ters of  shell,  are  thrown  back  so*  freely  by  such  pro- 
jectiles that  the  Italian  engineers,  after  practical  ex- 


158  Sea-coast  Fortresses. 

periments,  have  decided  95  feet  behind  the  platform 
to  be  not  an  excessive  distance  for  parados  exposed  to 
guns  of  a  larger  calibre  than  six  inches.  Up  to  and 
including  that  calibre  Q^  feet  proved  sufficient ;  field 
and  siege  guns  caused  no  dangerous  splinters.  But 
a  distance  of  95  feet  with  a  fall  of  15  degrees  calls  for 
a  parados  rising  at  least  25  feet  above  the  crest. 
Evidently  they  will  be  avoided  whenever  practicable, 
and,  when  unavoidable,  will  demand  special  studies 
in  each  case.  9 

Of  late  the  attention  of  engineers  has  been  strong- 
ly drawn  to  the  importance  of  concealing  sea-coast 
batteries  by  every  practicable  expedient.  To  in- 
crease precision  of  fire,  gunners  on  shipboard  will 
take  advantage  of  surrounding  objects  which  have  a 
known  relation  to  the  position  of  the  guns,  and  they 
will  correct  errors  in  pointing  by  noting  the  bursting 
of  percLission-shells,  or  columns  of  dust  thrown  up 
by  shot.  Hence  those  sites  are* most  advantageous 
which  do  not  favor  such  methods.  For  example, 
forests  behind  the  battery  give  an  uncertain  horizon, 
while  if  the  guns  are  clearly  defined  against  the  sky 
it  is  comparatively  easy  to  adjust  the  sights.  If  the 
slope  in  front  is  wooded  or  grown  up  with  brush  it  is 
not  easy  to  perceive  the  exact  point  where  a  projec- 
tile has  struck  ;  while  a  battery  placed  upon  a  long, 
smootli  slope  which  continues  to  rise  to  the  rear,  is  as 
unfavorably  situated  as  the  bull's  eye  of  a  target.  A 
battery  retired  a  short  distance  behind  the  crest  of  a 
bluff  affords  a  very  uncertain  clue  to  its  range.  A 
rocky  slope  increases  the  chance  of  ricochet  shots 
taking  effect,  while  a  steep  earthen  slope  stops  the 
projectiles. 

Evidently  in  the  future  we  must  sacrifice  neat 
crests  and  beautiful  slopes,  so  far  as  the  service  of  the 
guns  and  protection  against  washing  by  storms  will 
permit ;    trees  and  bushes   must  be  planted  on  the 


Fortification  of  the  Site  Selected.  159 

parapets  and  behind  the  batteries  to  prevent  a  clear 
definition  of  the  guns  ;  the  latter  themselves  must  be 
colored  to  harmonize  with  tlieir  surroundings  in  sum- 
mer and  winter ;  in  a  word,  dispersion  and  conceal- 
ment, as  contrasted  with  concentration  and  armor,  is 
the  hitest  phase  which  the  question  has  assumed. 
This  solutiou  has  been  strongly  advocated  by  Gen- 
eral Sir  Andrew  Clarke,  recently  Inspector-General 
of  Fortifications  in  England  ;  and  no  doubt,  as  ship- 
guns  improve  in  power  and  accuracy,  engineers  will 
study  every  expedient  to  aggravate  the  difficulty  of 
aiming  from  the  unstable  decks  to  which,  fortunately 
for  us,  they  are  confined. 

Another  matter  must  not  be  overlooked  in  con- 
structing batteries  for  high-power  guns — the  effect  of 
the  blast.  The  direct  blow  of  the  gases  is  not  so 
severe  as  might  be  expected.  A  smooth  layer  of 
stone  or  concrete  three  feet  thick,  under  and  in  front 
of  the  muzzle  of  a  12-inch  gun,  saves  the  parapet 
from  degradation  ;  but  there  is  another  effect  which 
in  confined  positions  is  formidable.  The  partial 
vacuum  created  behind  the  blast  has  a  tendency  to 
burst  open  doors  and  light  recesses,  break  windows, 
etc.,  by  the  pressure  of  the  air  behind  them.  This 
effect  has  long  been  noted  at  the  explosion  of  maga- 
zines. Iron  bars  2.5  inches  wide  and  0.5  inches  thick, 
securing  the  doors  of  shell  recesses,  are  reported  to 
have  been  bent  outward  by  the  vacuum  created  by  the 
blast  of  a  9-inch  rifled  gun.  Large  embrasures  in  case- 
mates have  caused  the  breaking  open  of  doors  of  shot- 
lifts,  and  have  shaken  uj)  the  cannoniers  most  un- 
pleasantly. To  meet  this  difficulty,  free  passages  for 
the  air  to  enter  should  be  supplied,  and  casemates 
should  never  be  closed  in  rear. 

Some  experiments  were  made  in  1872-73,  in  New 
York  harbor,  to  test  the  effect  of  the  blast  of  a  15- 
inch  smooth-bore  gun   charged  with  100  pounds  of 


160  Sea- coast  Fortresses. 

mammoth  j)owder  and  a  sliot  weigUing  460  pounds. 
The  conclusion  reached  by  the  Board  conducting  the 
experiments  was  that  a  second  battery  Q5  feet  below 
the  first  and  200  feet  in  advance,  the  ground  between 
being  a  somewhat  broken  slope  of  earth,  would  be 
beyond  the  range  of  injury  from  the  blast  or  from 
unburned  grains  of  powder ;  but  at  54  feet  in  front 
and  12  feet  below  the  muzzle  there  would  be  danger 
from  the  latter,  a  screen  of  inch  boards  having  been 
riddled  under  like  conditions.  It  was  also  inferred 
that  intermediate  irregularities  of  ground,  in  the  na- 
ture of  high  screens,  would  tend  to  further  reduce 
the  effects  of  the  blast  at  a  second  batter3^  and  that 
a  sufficiently  high  scarp  (height  not  determined) 
would  justify  placing  a  second  barbette  battery  at  its 
foot.  The  Board,  however,  guarded  itself  by  recom- 
mending that,  before  a  second  barbette  battery  was 
placed  in  front  of  the  high  battery,  "a  few  experi- 
mental shots  should  be  fired  in  order  to  test  the  force 
of  the  blast  at  points  of  the  intended  site." 

I  think  that,  with  the  high-power  guns  and  slow- 
burning  powder  of  to-day,  no  engineer  would  care  to 
dispose  two  barbette  batteries  so  that  one  should  fire 
over  the  other,  under  conditions  even  approaching 
those  favored  by  this  Board. 

In  fine,  then,  a  sea-coast  fortress  of  to-day,  suited 
to  the  needs  of  this  country,  consists  of  a  central 
keep  provided  with  bomb-proof  quarters  and  ar- 
ranged for  a  vigorous  defence  ;  of  detached  high- 
power  gun  batteries  (turrets,  iron  casemates,  lifts, 
barbette  batteries  for  disappearing  guns,  open  bar- 
bette batteries,  etc.,  according  to  circumstances), 
so  placed  as  to  sweep  the  channel  and  approaches, 
but  with  ample  space  between  their  sites  to  prevent 
mutual  interference  ;  of  detached  mortar  batteries, 
usually  in  rear  of  the  guns,  and,  so  far  as  possible,  out 
of  sight  of  the  enemy ;  of  machine  guns  in  covered 


Fortification  of  the  Site  Selected.  161 

positions  to  sweej)  slopes  and  approaches,  and  the  in- 
terior of  the  batteries  in  case  of  surprise  ;  of  wire  and 
other  entanglements  to  check  the  advance  of  tbe  es- 
calade parties  from  boats  ;  of  secure  operating  rooms, 
cable-shafts,  galleries,  and  flanking  guns  for  the 
mined  zones  ;  of  position-finders  suited  to  the  local- 
ity, for  determining  ranges  and  controlling  the  fire  of 
the  guns  and  the  operation  of  the  mines  from  the 
station  of  the  commanding  officer  ;  of  snitable  ar- 
rangements for  sweeping  the  approaches  by  the  elec- 
tric light,  and  for  using  movable  torpedoes  under 
control  from  the  shore.  In  countries  where  there  is 
danger  of  powerful  descents  upon  the  coast  more 
attention  is  paid  to  the  defence  of  the  position  against 
assault ;  but  with  us  little  is  to  be  feared  in  that  di- 
rection. Few  modern  fleets  could  afford  to  land  more 
than  1  500  or  2  000  men  for  that  purpose,  and,  with 
our  reserves  of  local  troops  added  to  the  regular  gar- 
rison, w^e  should  be  able  to  hold  the  works  with  the 
preparations  indicated. 

The  cost  of  such  a  fortress  is  less  than  might  be 
imagined,  and  very  far  less  than  would  be  demanded 
by  a  system  of  floating  batteries.  Thus  the  Fortifi- 
cation Board,  of  which  Secretary  Endicott  was  presi- 
dent, after  a  careful  study  of  the  subject,  estimated 
that  the  first  cost  of  one  floating  battery,  complete 
except  the  armament,  would  be  $3  300  000.  Let  us 
see  what  could  be  prepared  for  that  sum  in  the  way  of 
a  sea-coast  fortress,  adopting  a  liberal  scale  of  ex- 
penditure, increased  in  nearly  every  important  item 
over  the  figures  of  that  Board : 


162  Sea-coast  Fortresses. 

FIRST   COST  OF    A   SEA-COAST   FORTRESS   COMPLETE,  EX- 
CEPT THE   GUNS. 

One  2-gUTi  turret  for  two  16^-iiich  110- ton 

guns $1  000  000 

Ten  lifts  for  ten  12-incli  50- ton  guns 1  000  000 

Ten  disappearing  batteries  for  ten  12-inch 

50  ton  guns 450  000 

Three  batteries  for  forty-eight  12-inch  mor- 
tars          192  000 

Four  hundred  mines  and  cables,  etc.,  com- 
plete          200  000 

Two   operating  casemates   for   the   same, 

with  cable  shafts,  etc 100  000 

One  keep,  with  flanking  arrangements  for 

the  batteries 200  000 

Add  contingencies,  5  per  cent 158  000 

Total $3  300  000 

The  floating  battery  carries  two  16 J^ -inch  110- ton 
guns  and  one  10-inch  27- ton  gun,  and  is  exposed  to 
torpedo  attacks  and  to  rapid  deterioration.  The  fort- 
ress mounts  two  16;^ -inch  110- ton  guns,  twenty  12- 
inch  50-ton  guns,  forty-eight  12-incli  mortars,  four 
hundred  mines  with  their  adjuncts  ;  and  they  are  ex- 
posed neither  to  torpedo  attacks,  nor  to  escalade,  nor 
to  rapid  deterioration.  Bearing  in  mind  the  import- 
ance of  economy,  these  figures  permit  of  no  difference 
of  opinion  as  to  how  funds  should  be  invested  in 
cases  where  a  land  fortress  will  accomplish  the  de. 
sired  object ;  and  this  is  the  case  in  all  but  two  of 
our  cjiief  seaports. 

NAVAL   CO-OPERATION. 

We  have  seen  that,  from  the  standpoint  of  a  mili- 
tary engineer,  a  sea-coast  fortress  bears  a  relation  to 


Naval  Co-operation.  163 

the  naval  strength  of  the  nation  similar  (o  that  of 
an  entrenched  camp  to  *the  land  forces.  It  affords 
security  to  the  port  and  depots,  a  refuge  to  the  com- 
mercial marine,  and  a  base  of  operations  for  the  fleets. 
So  far  as  the  position  permits,  the  means  of  defence 
should  be  conflned  to  the  land  ;  in  that  way  only  can  -' 
economy,  permanency,  and  security  against  torpedo 
attacks  be  secured.  Moreover,  any  floating  defence 
is  always  liable  to  be  transferred  to  some  other  held 
to  meet  a  pressing  emergency,  real  or  imagined,  and 
the  enemy  may  thus  succeed  by  skilful  manoeuvres  in 
stripping  his  proposed  point  of  attack  of  elements 
vital  to  its  projected  plan  of  defence.  It  is  therefore 
an  accepted  axiom  with  us  that,  so  far  as  possible, 
our  system  of  land  defences  shall  be  independent  of 
floating  supx)ort. 

But  this,  like  all  other  rules,  has  its  exceptions. 
Thus,  for  example,  nature  may  offer  no  facilities  for 
defensive  works.  A  large  city,  like  many  of  our 
Lake  ports,  lying  upon  a  straight  shore  with  no  bay 
or  river  approach  admitting  of  defence  intervening 
between  itself  and  an  anchorage  within  bombarding 
range,  is  practically  at  the  mercy  of  the  power  hold- 
ing control  of  the  water.  Other  sites,  like  San  Fran-o 
Cisco  Bay,  by  reason  of  deep  water,  strong  currents, 
and  unfavorable  topography,  may  justify  the  great 
cost  of  floating  defences  to  complete  the  land  system. 
Yet  other  sites,  like  the  mouth  of  the  Mississippi,  '■ 
may  i^resent  engineering  difficulties  in  the  way  of 
foundations  which  render  it  cheaper  to  float  the 
heavy  guns  on  water  rather  than  on  mud. 

But  in  addition  to  these  special  cases  where  the 
aid  of  floating  batteries  is  counted  upon  by  the  land 
forces,  there  is  one  duty  of  vital  importance  in  a  vig- 
orous defence  which  is  solely  naval.  No  entrenched 
camp  would  be  left  without  outposts  to  watch  the 
approach  of  the  enemy,  or  without  sorties  to  harass 


164  Sea- coast  Fortresses. 

him  when  he  has  made  lijs  appearance.  Tlie  land 
defences  are  immovable  and  would  lose  half  their 
value  if  not  supported  by  an  active  naval  force.  It  is 
not  great  guns  that  we  shall  need  ;  they  can  usually 
be  mounted  far  more  economically  on  land.  It  is 
the  power  of  making  offensive  returns,  in  the  nature 
of  sorties,  that  we  lack  ;  and  for  supplementing  this 
deficiency  we  shall  everywhere  need  naval  co-opera- 
tion. Present  indications  lead  to  the  belief  that  the 
modern  torpedo-boat  is  lit  ted  for  this  work.  Its  high 
speed  would  render  it  as  useful  as  is  cavalry  for 
scouting  ;  its  terrible  weapon  would  make  it  more 
dreaded  than  the  '^  masked  battery"  so  often  heard 
of  in  the  early  days  of  the  civil  war ;  while  its 
power  of  combining  in  flotillas,  and  assailing  individ- 
ual armored  shi^^s  of  the  first-class  by  night  or  when 
obscured  by  the  smoke  of  their  own  guns,  might  lead 
to  results  as  decisive  as  those  achieved  by  the  column 
of  Macdonald  on  the  field  of  Wagram. 

These  needs  in  our  latest  system  of  coast  defences 
are  strongly  appreciated  by  engineers,  and  weliope 
that  they  may  be  seriously  considered  by  naval  offi- 
cers, who  will  know  how  they  can  best  be  met  by  ex- 
isting or  by  modified  types  of  torpedo-boats.  I  can- 
not but  believe  that  in  no  other  form  can  funds  for 
' '  coast  defenders  "be  so  usefully  applied.  O  ur  forts 
have  been  likened  to  chained  w^atch-dogs,  and  in  one 
sense  it  is  a  true  comparison  ;  but  we  must  not  forget 
that  the  dog  is  chained  in  front  of  the  office  safe, 
where  he  is  most  needed,  and  that  there  are  better 
ways  of  assisting  him  than  by  locking  an  unchained 
friend  in  the  same  apartment. 


INDEX. 


Alexandria,  bombardment  of,  24, 
33,  37,  38,  101. 

Armament  for  coast,  82. 

Armor,  kinds  compared,  142;  fab- 
rication of  the  Gruson,  143 ;  kind 
not  yet  adopted,  88,  90,  145 ;  re- 
sistance of  wrought  iron,  151; 
resistance  of  steel  and  compound, 
151;  resistance  of  chilled  cast 
iron,  152. 

Art  of  the  Engineer,  16. 

Attack  by  fleet,  nature  of,  40,  129, 
131,  134;  reasons  for,  137. 

Bombardment  distant,  the  prob- 
lem, 69;  effective  range,  70  ;  in- 
juries from,  72;  how  to  meet,  72, 
128. 

Boston,  strategic  relations  of,  12. 

Calibres  in  naval  warfare,  20. 

Casemates,  exposure  in,  63;  de- 
scription of,  89 ;  space  within,  90 ; 
how  to  locate,  156. 

Charleston,  naval  attack  on,  24,  28, 
136. 

Cost  of  Coast  defence,  judicious 
limit  of,  41;  estimate  for  chief 
ports,  44;  compared  with  insur- 
ance in  New  York,  45  ;  other 
reasons  for  incurring,  45,  52; 
proper  annual,  47;  analysis  for 
New  York  City,  49 ;  former  out- 
lays for,  51 ;  funds  how  applied, 
52;  fortresses  versus  "Coast  de- 
fenders," 161. 

Danube,  mortar-fire  on,  114. 


Disappearing  gun  batteries,  ex- 
posure in,  62;  description  of ,  95; 
merits  and  demerits,  94. 

Draught  of  war-ships,  20. 

Drewry's  Blufl",  naval  attack  on, 
27. 

Dutch  Gap,  mortar-fire  at,  104. 

Earth,  resistance  of,  149. 

Elements  of  Coast  defence,  19,  67, 
138,  153,  160. 

Formulae  approximate,  (see  Rules 
approximate). 

Forts  existing,  utility  of,  97,  141; 
history  of,  135;  description  of, 
138. 

Fort  Fisher,  naval  attack  on,  24, 
30,  90,  101. 

Fort  Sumter,  naval  attack  on,  28. 

Fortification  of  site,  discussion  of, 
153;  armament  for,  153;  plan- 
ning the  works,  154 ;  size  of  gar- 
rison, 155;  general  trace,  156; 
the  keep,  153;  traverses,  156; 
parados,  157;  concealment,  158; 
effect  of  blast,  159  ;  cost  of,  161. 

Grand  tactics,  in  Coast  defence,  14. 

Gulf  Coast,  strategic  relations  of, 
13. 

Guns,  mounting  analyzed,  55;  ex- 
posure without  parapet,  60;  ex- 
posure as  non-disappearing  bar- 
bette, 61 ;  exposure  on  the  King 
carriage,  62;  exposure  on  the 
Duane  gun-lift,  62;  exposure  in 
casemates,  63;  exposure  in  tur- 


166 


Index. 


ret,  63;  economic  comparison  of 
mountings,  64;  height  above  wa- 
ter, 73,  77;  modes  of  mounting, 
82,  85;  extreme  effective  range, 
70;  flanking  submarine  mines, 
96,  154;  power  of,  21;  calibres 
needed,  20;  number  of,  23; 
ashore  and  afloat,  25,  37;  ma- 
chine, 35,  98,  155;  rapid  firing, 
99;  relative  numbers,  153. 

Hampton  Roads,  strategic  relations 
of,  12. 

Horizontal  fire,  nnmber  required, 
83;  how  mounted,  85. 

Lifts  (gun),  exposure  in,  62;  de- 
scription of,  91. 

Lissa,  naval  attack  on,  33,  38,  101. 

Logistics  in  Coast  defence,  16. 

Machine  guns,  details  respecting,. 
98;  precision  of,  35;  for  local 
defence,  155. 

Magazines,  rules  for  constructing, 
91,  100;  explosion  of,  101. 

Masonry,  resistance  of,  146. 

Mortars,  number  required,  102; 
merits  of,  103;  demerits  of,  124; 
advantages  of  rifling,  105:  ve- 
locity of  fall,  106;  energy  to 
crush  deck,  106,  108;  efi:ective 
range^  109;  precision  of  fire,  109; 
practice  in  defences  of  Washing- 
ton, 110;  practice  at  Bucharest, 
111;  practice  at  Meppen,  112; 
practice  in  Russia,  113;  high  ex- 
plosives in,  114;  disposition  in 
battery,  119. 

Mortar  batteries,  plan  of,  118  ,  ser- 
vice of  ,.120;  distribution  of  fire, 
120;  cost  of,  124. 

Mortar  carriages,  Elswick,  116; 
Raskasoff,  117;  need  of  experi- 
ments with,  118. 

Mortar  platforms,  114;  Italian  ex- 
periments with,  115. 

Narragansect  Bay,  strategic  re- 
lations of ,  12. 


Naval  co-operation,  8,  68,  72,  131, 
162. 

Non-disappearing  gun  batteries, 
exposure  in,  61 ;  where  used,  95. 

Pacific  Coast,  strategic  relations  of, 
13. 

Parados,  157. 

Position-finders,  84. 

Pneumatic  dynamite  gun,  114, 133. 

Portland,  strategic  relations  of,  10. 

Port  Royal,  naval  attack  on,  37. 

Range-finders,  83, 

Rapid-firing  guns,  details  respect- 
ing, 99;  see  also  Machine  guns. 

Ricochet  fire.  73,  75. 

Rules  approximate,  weight  of  pro- 
jectile, 150;  velocity  of  projec- 
tile, 151;  energy  of  projectile, 
151;  penetration  of  wrought-iron 
armor,  151;  resistance  of  steel 
and  compound  armor,  151;  re- 
sistance of  chilled  cast-iron  ar- 
mor, 152. 

Sea-coast  fortresses,  discussed,  135 ; 
history  of  our,  135;  duty  of,  138; 
mir  third  system,  138;  our  pro- 
visional system  after  the  civil 
war,  141 ;  now  proposed,  153. 

Sebastopol,  naval  attack  on,  25. 

Ships  of  war,  draught  of,  20;  de- 
ployment of,  23;  guns  per  mile 
of  line,  24;  attack  on  land  de- 
fences, 40;  ranges  they  seek,  38; 
tactics  against  forts,  37;  deck 
protection,  103. 

Shrapnel  fire,  35. 

Site  for  works,  to  deter  bombard- 
ment, 69 ;  to  prevent  passage,  73 ; 
discussion  of  height,  73 ;  develop- 
ment of  front,  78;  submarine  re- 
quirements, 80;  selection  of,  67; 
see  also  Fortification  of  site. 

Spezzia,  defences  of,  15,  71. 

Strategy  naval,  in  Coast  defence, 
8,  13 ;  naval  bases  demanded  by, 
10. 


Index. 


167 


Submarine  mines,  depth  of  water, 
81:  inllueiice  of  eiirreiits,  80; 
tidal  range.  81 ;  conditions  to  ful- 
fil, 124,  138:  disposition  of,  130: 
detached  groups,  138;  self-act- 
ing, 138;  operating  casemate  for, 
131):  attacked  by  day,  129:  at- 
tacked by  night,  131;  ttanking 
guns  of,  l;)2:  electric  light  for, 
133;  movable  torpedoes  for,  133; 
passMu:^  throuiih,  by  force^  134, 


Torpedo-boats  (naval),  utility  of. 
14,  11),  54.  68,  73:  largo  numl)erj» 
needed,  108. 

Tori:)edoes,  movable,  conditions  to 
be  nu»t,  133. 

Travei-ses,  150. 

Turrets,  exposure  in.  OiJ;  descrip- 
tion of,  86:  metal  of,  88;  merit. s 
and  demerits  of,  88. 

Vertical  tiro,  discusst^d,  103:  theory 
of,  105,  109  'r  see  also  Mortars. 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

This  book  is  due  on  the  last  date  stamped  below, 
or  on  the  date  to  which  renewed.  Renewals  only: 

Tel.  No.  642-3405 
Renewals  may  be  made  4  days  prior  to  date  due. 
Renewed  books  are  subject  to  immediate  recall. 


I^PRlSlSTieT^ 


KfcC'DLO    AFR    l/t-4fHA0S 


"STANFORD 


m^M'm^m^ii 


OCT  8     1974 


IHRY2  5  1977 


SAN  niEGO-SlQ 


INTERLIBRARY  LOAN 

AUG    3  1978 


LD21A-50to-2,'71 
(P2001sl0)476 — A-32 


General  Library 

University  of  California 

Berkeley 


K  03n^l 


